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Natural Objects - nouns denoting natural objects (not man-made)

  1. Aar = a river in north central Switzerland that runs northeast into the Rhine
  2. Aare = a river in north central Switzerland that runs northeast into the Rhine
  3. Aare River = a river in north central Switzerland that runs northeast into the Rhine
  4. Abila = a promontory in northern Morocco opposite the Rock of Gibraltar
  5. Abukir = a bay on the Mediterranean Sea in northern Egypt
  6. Abukir Bay = a bay on the Mediterranean Sea in northern Egypt
  7. Abyla = a promontory in northern Morocco opposite the Rock of Gibraltar
  8. abysm = a bottomless gulf or pit
  9. abyss = a bottomless gulf or pit
  10. abyssal zone = the deep sea (2000 meters or more) where there is no light
  11. acclivity = an upward slope or grade
  12. Acheron = a river in Hades across which the souls of the dead were carried by Charon
  13. achondrite = a stony meteor lacking chondrules
  14. acicula = a needlelike part or structure of a plant or animal or crystal
  15. Aconcagua = the highest mountain in the western hemisphere
  16. Adam's Peak = a mountain peak in south central Sri Lanka
  17. Adams = a mountain peak in southwestern Washington in the Cascade Range
  18. Adige = a river in northern Italy that flows southeast into the Adriatic Sea
  19. Adirondack Mountains = a mountain range in northeastern New York State
  20. Adirondacks = a mountain range in northeastern New York State
  21. adjunct = something added to another thing but not an essential part of it
  22. Admiralty Range = mountains in Antarctica to the north of Victoria Land
  23. Adriatic = an arm of the Mediterranean between Slovenia and Croatia and Montenegro and Albania on the east and Italy on the west
  24. Adriatic Sea = an arm of the Mediterranean between Slovenia and Croatia and Montenegro and Albania on the east and Italy on the west
  25. Aegean = an arm of the Mediterranean between Greece and Turkey
  26. Aegean Sea = an arm of the Mediterranean between Greece and Turkey
  27. Aegospotami = a creek emptying into the Hellespont in present-day Turkey
  28. Aegospotamos = a creek emptying into the Hellespont in present-day Turkey
  29. aerie = the lofty nest of a bird of prey
  30. aerolite = a stony meteorite consisting of silicate minerals
  31. aery = the lofty nest of a bird of prey
  32. affluent = a branch that flows into the main stream
  33. Africa = the second largest continent
  34. agent = an active and efficient cause
  35. air bubble = a bubble of air
  36. airborne transmission = a transmission mechanism in the which the infectious agent is spread as an aerosol and usually enters a person through the respiratory tract
  37. Aire = a river in northern England that flows southeast through West Yorkshire
  38. Aire River = a river in northern England that flows southeast through West Yorkshire
  39. Alabama = a river in Alabama formed by the confluence of the Coosa and Tallapoosa Rivers near Montgomery
  40. Alabama River = a river in Alabama formed by the confluence of the Coosa and Tallapoosa Rivers near Montgomery
  41. Alaska Peninsula = a peninsula of southwestern Alaska
  42. Alaska Range = a mountain range in south central Alaska
  43. Aldebaran = the brightest star in Taurus
  44. Algol = the second brightest star in Perseus
  45. Alleghenies = the western part of the Appalachian Mountains
  46. Allegheny = a river that rises in Pennsylvania and flows north into New York and then back south through Pennsylvania again to join the Monongahela River at Pittsburgh which is the beginning of the Ohio River
  47. Allegheny Mountains = the western part of the Appalachian Mountains
  48. Allegheny River = a river that rises in Pennsylvania and flows north into New York and then back south through Pennsylvania again to join the Monongahela River at Pittsburgh which is the beginning of the Ohio River
  49. alluvial deposit = clay or silt or gravel carried by rushing streams and deposited where the stream slows down
  50. alluvial flat = a flat resulting from repeated deposits of alluvial material by running water
  51. alluvial plain = a flat resulting from repeated deposits of alluvial material by running water
  52. alluvial sediment = clay or silt or gravel carried by rushing streams and deposited where the stream slows down
  53. alluvion = clay or silt or gravel carried by rushing streams and deposited where the stream slows down
  54. alluvium = clay or silt or gravel carried by rushing streams and deposited where the stream slows down
  55. alp = any high mountain
  56. Alpha Centauri = brightest star in Centaurus
  57. Alpha Crucis = the brightest star in the Southern Cross
  58. Alpha Geminorum = a multiple star with 6 components; second brightest in Gemini
  59. Alpha Orionis = the second brightest star in Orion
  60. alpha particle = a positively charged particle that is the nucleus of the helium atom
  61. Alpine glacier = a glacier that moves down from a high valley
  62. Alpine type of glacier = a glacier that moves down from a high valley
  63. Alps = a large mountain system in south-central Europe
  64. Altai Mountains = a mountain range in central Asia that extends a thousand miles from Kazakhstan eastward into western Mongolia and northern China
  65. Altair = double star 15.7 light years from Earth
  66. Altay Mountains = a mountain range in central Asia that extends a thousand miles from Kazakhstan eastward into western Mongolia and northern China
  67. altocumulus = a cumulus cloud at an intermediate altitude of 2 or 3 miles
  68. altocumulus cloud = a cumulus cloud at an intermediate altitude of 2 or 3 miles
  69. altostratus = a stratus cloud at an intermediate altitude of 2 or 3 miles
  70. altostratus cloud = a stratus cloud at an intermediate altitude of 2 or 3 miles
  71. Amazon = a major South American river; arises in the Andes and flows eastward into the South Atlantic
  72. Amazon River = a major South American river; arises in the Andes and flows eastward into the South Atlantic
  73. America = North America and South America and Central America
  74. American Falls = a part of Niagara Falls in western New York
  75. ammonite = one of the coiled chambered fossil shells of extinct mollusks
  76. ammonoid = one of the coiled chambered fossil shells of extinct mollusks
  77. Amur = an Asian river between China and Russia
  78. Amur River = an Asian river between China and Russia
  79. Anapurna = a mountain in the Himalayas in Nepal
  80. Ancohuma = a mountain peak in the Andes in Bolivia
  81. Andaman Sea = part of the Bay of Bengal to the west of the Malay Peninsula
  82. Andes = a mountain range in South America running 5000 miles along the Pacific coast
  83. Andromeda = a constellation in the northern hemisphere between Cassiopeia and Pegasus
  84. Angara = a river in southeastern Siberia that flows northwest from Lake Baikal to become a tributary of the Yenisei River
  85. Angara River = a river in southeastern Siberia that flows northwest from Lake Baikal to become a tributary of the Yenisei River
  86. Angel = the highest waterfall; has more than one leap
  87. Angel Falls = the highest waterfall; has more than one leap
  88. anion = a negatively charged ion
  89. Annapurna = a mountain in the Himalayas in Nepal
  90. Antarctic continent = an extremely cold continent at the south pole almost entirely below the Antarctic Circle
  91. Antarctic Ocean = the southern waters surrounding Antarctica
  92. Antarctic Peninsula = a large peninsula of Antarctica that extends some 1200 miles north toward South America
  93. Antarctica = an extremely cold continent at the south pole almost entirely below the Antarctic Circle
  94. Antares = the brightest star in Scorpius
  95. anthill = a mound of earth made by ants as they dig their nest
  96. antibaryon = the antiparticle of a baryon
  97. antielectron = an elementary particle with positive charge
  98. antilepton = the antiparticle of a lepton
  99. antimeson = the antiparticle of a meson
  100. antimuon = the antiparticle of a muon
  101. antineutrino = the antiparticle of a neutrino
  102. antineutron = the antiparticle of a neutron
  103. antiparticle = a particle that has the same mass as another particle but has opposite values for its other properties
  104. antiproton = an unstable negatively charged proton
  105. antiquark = the antiparticle of a quark
  106. antitauon = an antilepton of very great mass
  107. Antlia = a faint constellation in the southern hemisphere near Hydra and Vela
  108. Apalachicola = a river in northwestern Florida formed by the confluence of the Chattahoochee River and the Flint River at the Florida border
  109. Apalachicola River = a river in northwestern Florida formed by the confluence of the Chattahoochee River and the Flint River at the Florida border
  110. Apennines = a mountain range extending the length of the Italian peninsula
  111. aperture = a natural opening in something
  112. Apollo asteroid = an asteroid whose orbit crosses the Earth's orbit
  113. Appalachian Mountains = a mountain range in the eastern United States extending from Quebec to the Gulf of Mexico
  114. Appalachians = a mountain range in the eastern United States extending from Quebec to the Gulf of Mexico
  115. Apus = a constellation in the polar region of the southern hemisphere near Octans
  116. Aquarius = a zodiacal constellation in the southern hemisphere
  117. aquifer = underground bed or layer yielding ground water for wells and springs etc
  118. Aquila = a constellation in the Milky Way near Cygnus
  119. Ara = a constellation in the southern hemisphere near Telescopium and Norma
  120. Arabian Gulf = a shallow arm of the Arabian Sea between Iran and the Arabian peninsula
  121. Arabian Sea = a northwestern arm of the Indian Ocean between India and Arabia
  122. Arafura Sea = a part of the western Pacific Ocean to the north of Australia and to the south of New Guinea and the eastern islands of Indonesia
  123. Araguaia = a river in central Brazil that flows generally northward (with many falls) to join the Tocantins River
  124. Araguaia River = a river in central Brazil that flows generally northward (with many falls) to join the Tocantins River
  125. Araguaya = a river in central Brazil that flows generally northward (with many falls) to join the Tocantins River
  126. Araguaya River = a river in central Brazil that flows generally northward (with many falls) to join the Tocantins River
  127. Aral Sea = a lake to the east of the Caspian Sea lying between Kazakhstan and Uzbekistan
  128. Ararat = the mountain peak that Noah's ark landed on as the waters of the great flood receded
  129. Aras = a river that rises in northeastern Turkey (near the source of the Euphrates) and flows generally eastward through Armenia to the Caspian Sea
  130. Arauca = a river that rises in northern Colombia and flows generally eastward to the Orinoco in central Venezuela
  131. Araxes = a river that rises in northeastern Turkey (near the source of the Euphrates) and flows generally eastward through Armenia to the Caspian Sea
  132. archeological remains = a relic that has been excavated from the soil
  133. archipelago = a group of many islands in a large body of water
  134. Arctic Ocean = ice covered waters surrounding the North Pole
  135. Arcturus = the 4th brightest star and the brightest star in the constellation Bootes
  136. arete = a sharp narrow ridge found in rugged mountains
  137. Argo = formerly a large constellation in the southern hemisphere between Canis Major and the Southern Cross
  138. Argun = a river in eastern Asia that arises in China and flows northeast along the border between China and Russia to become a tributary of the Amur River
  139. Argun River = a river in eastern Asia that arises in China and flows northeast along the border between China and Russia to become a tributary of the Amur River
  140. Aries = a small zodiacal constellation in the northern hemisphere
  141. Aristarchus = a bright crater on the Moon
  142. Arkansas = a river that rises in the Rocky Mountains in Colorado and flows southeast through Kansas and Oklahoma and through Arkansas to become a tributary of the Mississippi River
  143. Arkansas River = a river that rises in the Rocky Mountains in Colorado and flows southeast through Kansas and Oklahoma and through Arkansas to become a tributary of the Mississippi River
  144. Arno = a river in central Italy rising in the Apennines and flowing through Florence and Pisa to the Ligurian Sea
  145. Arno River = a river in central Italy rising in the Apennines and flowing through Florence and Pisa to the Ligurian Sea
  146. arroyo = a stream or brook
  147. ascent = an upward slope or grade
  148. Asia = the largest continent with 60% of the earth's population; it is joined to Europe on the west to form Eurasia
  149. asterism = a cluster of stars
  150. asteroid = any of numerous small celestial bodies composed of rock and metal that move around the sun
  151. Asterope = one of the stars in the star cluster Pleiades
  152. asthenosphere = the lower layer of the crust
  153. Atacama Trench = a depression in the floor of the Pacific Ocean off the coast of Chile
  154. Atlantic = the 2nd largest ocean
  155. Atlantic Coast = a coast of the Atlantic Ocean
  156. Atlantic Ocean = the 2nd largest ocean
  157. Atlas Mountains = a mountain range in northern Africa between the Mediterranean and the Sahara Desert
  158. atmosphere = the envelope of gases surrounding any celestial body
  159. atoll = an island consisting of a circular coral reef surrounding a lagoon
  160. Auriga = a conspicuous constellation in the northern hemisphere
  161. Australia = the smallest continent
  162. Australian Alps = a range of mountains in Australia that forms the southern end of the Great Dividing Range
  163. Avon = a river in central England that flows through Stratford-on-Avon and empties into the Severn / a river in southwestern England rising in Gloucestershire and flowing through Bristol to empty into the estuary of the Severn
  164. b-meson = exceedingly short-lived meson
  165. backwater = a body of water that was created by a flood or tide or by being held or forced back by a dam
  166. badlands = deeply eroded barren land
  167. Baffin Bay = a body of water between Greenland and northeastern Canada; connected with the Arctic Ocean to the north and with the Atlantic Ocean (via the Labrador Sea) to the south
  168. Baikal = the largest freshwater lake in Asia or Europe and the deepest lake in the world
  169. Baja California = a mountainous peninsula on northwest Mexico
  170. Balaton = a large shallow lake in western Hungary
  171. Balkan Mountain Range = the major mountain range of Bulgaria and the Balkan Peninsula
  172. Balkan Mountains = the major mountain range of Bulgaria and the Balkan Peninsula
  173. Balkans = the major mountain range of Bulgaria and the Balkan Peninsula
  174. Baltic = a sea in northern Europe
  175. Baltic Sea = a sea in northern Europe
  176. bank = a long ridge or pile / sloping land (especially the slope beside a body of water) / a slope in the turn of a road or track
  177. bar = a submerged (or partly submerged) ridge in a river or along a shore
  178. barbecue pit = a pit where wood or charcoal is burned to make a bed of hot coals suitable for barbecuing meat
  179. Barents Sea = the part of the Arctic Ocean to the north of Norway and Russia
  180. barrier = anything serving to maintain separation by obstructing vision or access
  181. barrier island = a long narrow sandy island (wider than a reef) running parallel to the shore
  182. barrier reef = a long coral reef near and parallel to the shore
  183. baryon = any of the elementary particles having a mass equal to or greater than that of a proton and that participate in strong interactions
  184. base = the bottom or lowest part
  185. basin = a natural depression in the surface of the land often with a lake at the bottom of it
  186. bathyal district = the steep descent of the seabed from the continental shelf to the abyssal zone
  187. bathyal zone = the steep descent of the seabed from the continental shelf to the abyssal zone
  188. bay = an indentation of a shoreline larger than a cove but smaller than a gulf
  189. Bay of Bengal = an arm of the Indian Ocean to the east of India
  190. Bay of Biscay = an arm of the Atlantic Ocean in western Europe
  191. Bay of Campeche = a part of the Gulf of Mexico to the west of Yucatan
  192. Bay of Fundy = a bay of the North Atlantic between New Brunswick and Nova Scotia
  193. Bay of Naples = an arm of the Tyrrhenian Sea at Naples
  194. Bay of Ob = an inlet of the Kara Sea in western Siberia
  195. Baykal = the largest freshwater lake in Asia or Europe and the deepest lake in the world
  196. bayou = a swampy arm or slow-moving outlet of a lake
  197. beach = an area of sand sloping down to the water of a sea or lake
  198. beachfront = a strip of land running along a beach
  199. Beaufort Sea = part of the Arctic Ocean to the northeast of Alaska
  200. beauty quark = a quark with a charge of -1/3 and a mass about 10,000 times that of an electron
  201. bed = a depression forming the ground under a body of water / (geology) a stratum of rock
  202. bedrock = solid unweathered rock lying beneath surface deposits of soil
  203. beehive = a structure that provides a natural habitation for bees
  204. belay = something to which a mountain climber's rope can be secured
  205. belt = a path or strip
  206. ben = a mountain or tall hill
  207. bench = a level shelf of land interrupting a declivity
  208. berg = a large mass of ice floating at sea
  209. Bering Sea = part of the North Pacific between Alaska and Siberia
  210. Bering Strait = a strait connecting the Bering Sea to the Arctic Ocean
  211. Berkshire Hills = a low mountain range in western Massachusetts
  212. Berkshires = a low mountain range in western Massachusetts
  213. berm = a narrow ledge or shelf typically at the top or bottom of a slope
  214. Beta Centauri = the second brightest star in Centaurus
  215. Beta Crucis = the second brightest star in the Southern Cross
  216. Beta Orionis = the brightest star in Orion
  217. beta particle = a high-speed electron or positron emitted in the decay of a radioactive isotope
  218. Betelgeuse = the second brightest star in Orion
  219. Big Dipper = a group of seven bright stars in the constellation Ursa Major
  220. Big Sioux River = a river that rises in northeastern South Dakota and flows southward to join the Missouri River at Sioux City, Iowa
  221. Bighorn = a river that flows from central Wyoming to the Yellowstone River in southern Montana
  222. Bighorn River = a river that flows from central Wyoming to the Yellowstone River in southern Montana
  223. bight = a broad bay formed by an indentation in the shoreline
  224. Bight of Benin = a broad indentation of the Gulf of Guinea in western Africa
  225. bilestone = a calculus formed in the gall bladder or its ducts
  226. billabong = a branch of a river made by water flowing from the main stream only when the water level is high / a stagnant pool of water in the bed of a stream that flows intermittently
  227. binary = a system of two stars that revolve around each other under their mutual gravitation
  228. binary star = a system of two stars that revolve around each other under their mutual gravitation
  229. biohazard = any bacterium or virus or toxin that could be used in biological warfare
  230. biological agent = any bacterium or virus or toxin that could be used in biological warfare
  231. bird nest = nest where birds lay their eggs and hatch their young
  232. bird's nest = nest where birds lay their eggs and hatch their young
  233. birdnest = nest where birds lay their eggs and hatch their young
  234. Biscayne Bay = a narrow bay formed by an inlet from the Atlantic Ocean in southeastern Florida
  235. Bismarck Sea = an arm of the South Pacific to the southwest of the Bismarck Archipelago
  236. bit = a small fragment of something broken off from the whole
  237. black body = a hypothetical object capable of absorbing all the electromagnetic radiation falling on it
  238. Black Forest = a hilly forest region in southwestern Germany
  239. Black Hills = mountains in southwestern South Dakota and northeastern Wyoming; sacred to the Sioux
  240. black hole = a region of space resulting from the collapse of a star
  241. Black Sea = a sea between Europe and Asia
  242. blackbody = a hypothetical object capable of absorbing all the electromagnetic radiation falling on it
  243. bladder stone = a calculus formed in the bladder
  244. blade = something long and thin resembling a blade of grass
  245. blanket = anything that covers
  246. blood-brain barrier = a mechanism that creates a barrier between brain tissues and circulating blood
  247. blue = the sky as viewed during daylight
  248. blue air = the sky as viewed during daylight
  249. Blue Nile = a headstream of the Nile
  250. Blue Ridge = a range of the Appalachians extending from southern Pennsylvania to northern Georgia
  251. Blue Ridge Mountains = a range of the Appalachians extending from southern Pennsylvania to northern Georgia
  252. blue sky = the sky as viewed during daylight
  253. bluff = a high steep bank
  254. Bo Hai = an inlet of the Yellow Sea, on the coast of Eastern China
  255. Bodensee = a lake in southeastern Germany on the northern side of the Swiss Alps
  256. body = an individual 3-dimensional object that has mass and that is distinguishable from other objects
  257. body of water = the part of the earth's surface covered with water
  258. bog = wet spongy ground of decomposing vegetation; has poorer drainage than a swamp
  259. bolt-hole = a hole through which an animal may bolt when pursued into its burrow or den
  260. bonanza = an especially rich vein of precious ore
  261. Bonete = a mountain in the Andes in Argentina
  262. Bootes = a constellation in the northern hemisphere near Ursa Major
  263. borrow pit = a pit created to provide earth that can be used as fill at another site
  264. boson = any particle that obeys Bose-Einstein statistics but not the Pauli exclusion principle
  265. Bosporus = a strait connecting the Mediterranean and the Black Sea; separates the European and Asian parts of Turkey
  266. bottom = a depression forming the ground under a body of water / low-lying alluvial land near a river
  267. bottom quark = a quark with a charge of -1/3 and a mass about 10,000 times that of an electron
  268. bottomland = low-lying alluvial land near a river
  269. Bougainville Trench = a depression in the floor of the Pacific Ocean between New Guinea and the Solomon Islands
  270. boulder = a large smooth mass of rock detached from its place of origin
  271. bowlder = a large smooth mass of rock detached from its place of origin
  272. brae = a slope or hillside
  273. Brahmaputra = an Asian river
  274. Brahmaputra River = an Asian river
  275. branch = a stream or river connected to a larger one
  276. branched chain = an open chain of atoms with one or more side chains attached to it
  277. Brazos = a river that rises in Mexico and flows across Texas into the Gulf of Mexico
  278. Brazos River = a river that rises in Mexico and flows across Texas into the Gulf of Mexico
  279. breach = an opening
  280. break = a crack in the earth's crust resulting from the displacement of one side with respect to the other
  281. Brenner Pass = an Alpine mountain pass connecting Innsbruck in Austria with Bolzano in Italy that has long been a route for trade and for invasions
  282. brickbat = a fragment of brick used as a weapon
  283. briny = any very large body of (salt) water
  284. Bristol Channel = an inlet of the Atlantic Ocean between southern Wales and southwestern England
  285. brook = a natural stream of water smaller than a river
  286. brooklet = a small brook
  287. bubble = a hollow globule of gas
  288. buffalo chip = a piece of dried bovine dung
  289. building block = a single undivided natural thing occurring in the composition of something else
  290. bullet hole = a hole made by a bullet passing through it
  291. burrow = a hole made by an animal, usually for shelter
  292. butte = a hill that rises abruptly from the surrounding region
  293. Buzzards Bay = an inlet of the Atlantic Ocean in southeastern Massachusetts
  294. Cachi = a mountain in the Andes in Argentina
  295. Caelum = a constellation in the southern hemisphere near Columba and Eridanus
  296. calculus = a hard lump produced by the concretion of mineral salts
  297. caldera = a large crater caused by the violent explosion of a volcano that collapses into a depression
  298. Callisto = the second largest of Jupiter's satellites
  299. Caloosahatchee = a river in southern Florida that flows westerly to the Gulf of Mexico
  300. Caloosahatchee River = a river in southern Florida that flows westerly to the Gulf of Mexico
  301. Cam = a river in east central England that flows past Cambridge to join the Ouse River
  302. Cam River = a river in east central England that flows past Cambridge to join the Ouse River
  303. camber = a slope in the turn of a road or track
  304. Cambrian Mountains = a rugged plateau that runs north to south through central Wales
  305. Canadian = a river rising in northeastern New Mexico and flowing eastward across the Texas panhandle to become a tributary of the Arkansas River in Oklahoma
  306. Canadian Falls = a part of Niagara Falls in Ontario
  307. Canadian River = a river rising in northeastern New Mexico and flowing eastward across the Texas panhandle to become a tributary of the Arkansas River in Oklahoma
  308. canal = an indistinct surface feature of Mars once thought to be a system of channels
  309. Canandaigua Lake = a glacial lake in central New York
  310. Cancer = a small zodiacal constellation in the northern hemisphere
  311. cancer body = an inclusion body found in plasma cells in cases of cancer
  312. Canicula = the brightest star in the sky
  313. Canis Major = a constellation to the southeast of Orion
  314. Canis Minor = a constellation to the east of Orion
  315. canon = a ravine formed by a river in an area with little rainfall
  316. Canopus = supergiant star 650 light years from Earth
  317. cant = a slope in the turn of a road or track
  318. Cantabrian Mountains = a range of mountains in northern Spain along the coast of the Bay of Biscay
  319. Canton River = a river in southeast China that flows into the South China Sea
  320. canyon = a ravine formed by a river in an area with little rainfall
  321. canyonside = the steeply sloping side of a canyon
  322. cap = a protective covering that is part of a plant
  323. cape = a strip of land projecting into a body of water
  324. Cape Canaveral = a sandy promontory (formerly Cape Kennedy) extending into the Atlantic Ocean from a barrier island off the eastern coast of Florida
  325. Cape Cod Bay = the southern part of Massachusetts Bay
  326. Cape Fear River = a river in North Carolina that flows southeast to the Atlantic Ocean at Cape Fear
  327. Cape Kennedy = a sandy promontory (formerly Cape Kennedy) extending into the Atlantic Ocean from a barrier island off the eastern coast of Florida
  328. Cape Sable = a promontory on the far southern part of Nova Scotia / a cape at the southwest tip of Florida
  329. Cape Trafalgar = a small cape in southwestern Spain
  330. Cape York = the northern tip of Cape York Peninsula at the Torres Strait
  331. Cape York Peninsula = a peninsula in Queensland in northeastern Australia between the Gulf of Carpentaria and the Coral Sea
  332. Capella = the brightest star in Auriga
  333. Capricorn = a faint zodiacal constellation in the southern hemisphere
  334. Capricornus = a faint zodiacal constellation in the southern hemisphere
  335. Caribbean = an arm of the Atlantic Ocean between North and South America
  336. Caribbean Sea = an arm of the Atlantic Ocean between North and South America
  337. Carina = a keel-shaped constellation in the southern hemisphere
  338. Carlsbad Caverns = a group of caverns in southeastern New Mexico noted for their stalactites and stalagmites
  339. Carpathian Mountains = a mountain range in central Europe that extends from Slovakia and southern Poland southeastward through western Ukraine to northeastern Romania
  340. Carpathians = a mountain range in central Europe that extends from Slovakia and southern Poland southeastward through western Ukraine to northeastern Romania
  341. Carpentaria = a wide shallow inlet of the Arafura Sea in northern Australia
  342. carpet = a natural object that resembles or suggests a carpet
  343. cascade = a small waterfall or series of small waterfalls
  344. Cascade Mountains = a mountain range in the northwestern United States extending through Washington and Oregon and northern California
  345. Cascade Range = a mountain range in the northwestern United States extending through Washington and Oregon and northern California
  346. Cascades = a mountain range in the northwestern United States extending through Washington and Oregon and northern California
  347. Caspian = a large saltwater lake between Iran and Russia fed by the Volga River
  348. Caspian Sea = a large saltwater lake between Iran and Russia fed by the Volga River
  349. Cassiopeia = a W-shaped constellation in the northern hemisphere near Polaris
  350. Castor = a multiple star with 6 components; second brightest in Gemini
  351. cataract = a large waterfall
  352. Cataract Canyon = a tributary of the Grand Canyon
  353. catch = anything that is caught
  354. cation = a positively charged ion
  355. Catskill Mountains = a range of the Appalachians to the west of the Hudson in southeastern New York
  356. Catskills = a range of the Appalachians to the west of the Hudson in southeastern New York
  357. Caucasus = the mountain range in Caucasia between the Black Sea and the Caspian Sea that forms part of the traditional border between Europe and Asia
  358. Caucasus Mountains = the mountain range in Caucasia between the Black Sea and the Caspian Sea that forms part of the traditional border between Europe and Asia
  359. cave = a geological formation consisting of an underground enclosure with access from the surface of the ground or from the sea
  360. cavern = a large cave or a large chamber in a cave / any large dark enclosed space
  361. cavity = a sizeable hole
  362. cay = a coral reef off the southern coast of Florida
  363. Cayuga Lake = a glacial lake in central New York
  364. celestial body = natural objects visible in the sky
  365. cellular inclusion = any small intracellular body found within another
  366. Centaur = a conspicuous constellation in the southern hemisphere near the Southern Cross
  367. Centaurus = a conspicuous constellation in the southern hemisphere near the Southern Cross
  368. Cepheus = a faint constellation in the northern hemisphere near Cassiopeia and the pole star
  369. Ceres = the largest asteroid and the first discovered
  370. Cetus = a large constellation on the equator near Pisces and Aquarius
  371. Chad = a lake in north central Africa
  372. chain = a series of linked atoms (generally in an organic molecule) / a series of hills or mountains
  373. chain of mountains = a series of hills or mountains
  374. Chamaeleon = a faint constellation in the polar region of the southern hemisphere near Apus and Mensa
  375. Chameleon = a faint constellation in the polar region of the southern hemisphere near Apus and Mensa
  376. champaign = extensive tract of level open land
  377. Champlain = a lake in northeastern New York, northwestern Vermont and southern Quebec
  378. Chang = the longest river of Asia
  379. Chang Jiang = the longest river of Asia
  380. Changjiang = the longest river of Asia
  381. Changtzu = a mountain in the central Himalayas on the border of Tibet and Nepal
  382. channel = a deep and relatively narrow body of water (as in a river or a harbor or a strait linking two larger bodies) that allows the best passage for vessels
  383. Chao Phraya = a river in Thailand formed by the confluence of the Nan and Ping Rivers
  384. chap = a crack in a lip caused usually by cold
  385. Chari = an African river that flows northwest into Lake Chad
  386. Chari River = an African river that flows northwest into Lake Chad
  387. Charioteer = a conspicuous constellation in the northern hemisphere
  388. Charles = a river in eastern Massachusetts that empties into Boston Harbor and that separates Cambridge from Boston
  389. Charles River = a river in eastern Massachusetts that empties into Boston Harbor and that separates Cambridge from Boston
  390. Charles's Wain = a group of seven bright stars in the constellation Ursa Major
  391. charm quark = a quark with an electric charge of +2/3 and a mass 2900 times that of an electron and a charm of +1
  392. chasm = a deep opening in the earth's surface
  393. Chattahoochee = a river rising in northern Georgia and flowing southwest and south to join the Flint River at the Florida border where they form the Apalachicola River
  394. Chattahoochee River = a river rising in northern Georgia and flowing southwest and south to join the Flint River at the Florida border where they form the Apalachicola River
  395. chemical chain = a series of linked atoms
  396. Chesapeake Bay = a large inlet of the North Atlantic between Virginia and Maryland
  397. Chimborazo = a mountain peak in the Andes in Ecuador
  398. chink = a narrow opening as e.g. between planks in a wall
  399. chip = a small fragment of something broken off from the whole / a piece of dried bovine dung
  400. Chiron = an asteroid discovered in 1977
  401. chondrite = a rock of meteoric origin containing chondrules
  402. chondrule = small granule (of e.g. chrysolite) found in some meteoric rocks
  403. chromosphere = a gaseous layer of the sun's atmosphere (extending from the photosphere to the corona) that is visible during a total eclipse of the sun
  404. Chu Kiang = a river in southeast China that flows into the South China Sea
  405. chuckhole = a pit or hole produced by wear or weathering
  406. Chukchi Peninsula = peninsula of northeastern Siberia across the Bering Strait from northwestern Alaska
  407. Chukchi Sea = part of the Arctic Ocean just to the north of the Bering Strait
  408. Cimarron = a river that rises in northeastern New Mexico and flows eastward into Oklahoma where it becomes a tributary of the Arkansas River
  409. Cimarron River = a river that rises in northeastern New Mexico and flows eastward into Oklahoma where it becomes a tributary of the Arkansas River
  410. cinder = a fragment of incombustible matter left after a wood or coal or charcoal fire
  411. Circinus = a small faint constellation in the southern hemisphere near Musca and Triangulum Australe
  412. cirque = a steep-walled semicircular basin in a mountain
  413. cirrocumulus = a cloud at a high altitude consisting of a series of regularly arranged small clouds resembling ripples
  414. cirrocumulus cloud = a cloud at a high altitude consisting of a series of regularly arranged small clouds resembling ripples
  415. cirrostratus = a thin uniform layer of hazy cloud at high altitude
  416. cirrostratus cloud = a thin uniform layer of hazy cloud at high altitude
  417. cirrus = a wispy white cloud (usually of fine ice crystals) at a high altitude
  418. cirrus cloud = a wispy white cloud (usually of fine ice crystals) at a high altitude
  419. clast = a constituent fragment of a clastic rock
  420. clastic rock = a rock composed of broken pieces of older rocks
  421. cleft = a long narrow opening
  422. cliff = a steep high face of rock
  423. climb = an upward slope or grade
  424. Clinch River = a river that rises in southwestern Virginia and flows generally southwestward across eastern Tennessee to the Tennessee River
  425. clinker = a fragment of incombustible matter left after a wood or coal or charcoal fire
  426. closed chain = a chain of atoms in a molecule that forms a closed loop
  427. closed universe = a universe that is spatially closed and in which there is sufficient matter to halt the expansion that began with the big bang
  428. cloud = a visible mass of water or ice particles suspended at a considerable altitude
  429. cloud bank = a layer of clouds seen from a distance
  430. Clyde = a river in western Scotland that flows from the southern uplands into the Firth of Clyde
  431. coal = a hot fragment of wood or coal that is left from a fire and is glowing or smoldering
  432. coast = a slope down which sleds may coast / the shore of a sea or ocean
  433. Coast Mountains = a string of mountain ranges along the Pacific coast of North America from southeastern Alaska to Lower California
  434. Coast Range = a string of mountain ranges along the Pacific coast of North America from southeastern Alaska to Lower California
  435. coastal plain = a plain adjacent to a coast
  436. coastland = land in a coastal area
  437. Cocytus = a river in Hades that was said to be a tributary of the Acheron
  438. Coeur d'Alene Lake = a lake in northern Idaho
  439. coffee grounds = the dregs remaining after brewing coffee
  440. col = a pass between mountain peaks
  441. collector = a crater that has collected cosmic material hitting the earth
  442. collision course = a course of a moving object that will lead to a collision if it continues unchanged
  443. Colorado = an important river in the southwestern United States; rises in the Rocky Mountains of northern Colorado and flows southwest through Utah into Arizona (where it flows through the Grand Canyon) and then southward through the southern tip of Nevada, then forming the border between California and Arizona and finally into Mexico where it empties into the Gulf of California; the main source of water in the southwestern United States / a river in Texas
  444. Colorado Plateau = a large plateau to the south and west of the Rocky Mountains; abuts mountains on the north and east and ends in an escarpment overlooking lowlands to the south and west
  445. Colorado River = an important river in the southwestern United States; rises in the Rocky Mountains of northern Colorado and flows southwest through Utah into Arizona (where it flows through the Grand Canyon) and then southward through the southern tip of Nevada, then forming the border between California and Arizona and finally into Mexico where it empties into the Gulf of California; the main source of water in the southwestern United States / a river in Texas
  446. Columba = a constellation in the southern hemisphere near Puppis and Caelum
  447. Columbia = a North American river; rises in southwestern Canada and flows southward across Washington to form the border between Washington and Oregon before emptying into the Pacific
  448. Columbia River = a North American river; rises in southwestern Canada and flows southward across Washington to form the border between Washington and Oregon before emptying into the Pacific
  449. coma = the luminous cloud of particles surrounding the frozen nucleus of a comet
  450. Coma Berenices = a constellation in the northern hemisphere between Ursa Major and Bootes
  451. comet = a relatively small extraterrestrial body consisting of a frozen mass that travels around the sun in a highly elliptical orbit
  452. commemorative = an object (such as a coin or postage stamp) made to mark an event or honor a person
  453. common fault = an inclined fault in which the hanging wall appears to have slipped downward relative to the footwall
  454. Communism Peak = the highest mountain peak in the Pamir Mountains
  455. concretion = a hard lump produced by the concretion of mineral salts
  456. condensation trail = an artificial cloud created by an aircraft
  457. confluent = a branch that flows into the main stream
  458. Congo = a major African river
  459. Congo River = a major African river
  460. Connecticut = a river in the northeastern United States
  461. Connecticut River = a river in the northeastern United States
  462. consolidation = something that has consolidated into a compact mass
  463. Constance = a lake in southeastern Germany on the northern side of the Swiss Alps
  464. constellation = a configuration of stars as seen from the earth
  465. continent = one of the large landmasses of the earth
  466. continental glacier = a glacier that spreads out from a central mass of ice
  467. continental shelf = the relatively shallow (up to 200 meters) seabed surrounding a continent
  468. continental slope = the steep descent of the seabed from the continental shelf to the abyssal zone
  469. contrail = an artificial cloud created by an aircraft
  470. Cook Strait = a narrow strait separating the North Island and South Island in New Zealand
  471. Coosa = river that rises in northwestern Georgia and flows southwest through eastern Alabama to join the Tallapoosa River near Montgomery and form the Alabama River
  472. Coosa River = river that rises in northwestern Georgia and flows southwest through eastern Alabama to join the Tallapoosa River near Montgomery and form the Alabama River
  473. Copernicus = a conspicuous crater on the Moon
  474. coprolite = fossil excrement
  475. coprolith = a hard mass of fecal matter
  476. coral reef = a reef consisting of coral consolidated into limestone
  477. Coral Sea = an arm of the South Pacific to the northeast of Australia
  478. core = the central part of the Earth / a cylindrical sample of soil or rock obtained with a hollow drill
  479. corner = a projecting part where two sides or edges meet
  480. Corona Borealis = a small constellation in the northern hemisphere between Bootes and Hercules
  481. Coropuna = a mountain peak in the Andes in Peru
  482. corrie = a steep-walled semicircular basin in a mountain
  483. Corvus = a small quadrilateral constellation in the southern hemisphere near Virgo
  484. cosmic string = a hypothetical one-dimensional subatomic particle having a concentration of energy and the dynamic properties of a flexible loop
  485. cosmos = everything that exists anywhere
  486. couple = something joined by two equal and opposite forces that act along parallel lines
  487. course = a line or route along which something travels or moves
  488. cove = a small inlet / small or narrow cave in the side of a cliff or mountain
  489. cover = a natural object that covers or envelops
  490. covering = a natural object that covers or envelops
  491. cow chip = a piece of dried bovine dung
  492. cow dung = a piece of dried bovine dung
  493. Crab Nebula = a remnant of a supernova detected first in 1054 AD
  494. crack = a long narrow opening
  495. crag = a steep rugged rock or cliff
  496. Crane = a small constellation in the southern hemisphere near Phoenix
  497. cranny = a small opening or crevice
  498. crater = a bowl-shaped depression formed by the impact of a meteorite or bomb / a faint constellation in the southern hemisphere near Hydra and Corvus / a bowl-shaped geological formation at the top of a volcano
  499. craton = the part of a continent that is stable and forms the central mass of the continent
  500. creation = everything that exists anywhere
  501. creek = a natural stream of water smaller than a river
  502. creek bed = a channel occupied (or formerly occupied) by a stream
  503. crevasse = a deep fissure
  504. crevice = a long narrow opening
  505. Crocodile River = an African river
  506. Cross-Florida Waterway = a waterway used by small boats to travel between the Atlantic Ocean and the Gulf of Mexico through Lake Okeechobee and the Caloosahatchee Canal and the Caloosahatchee River
  507. crossing = a shallow area in a stream that can be forded
  508. Crow = a small quadrilateral constellation in the southern hemisphere near Virgo
  509. crust = the outer layer of the Earth / a hard outer layer that covers something
  510. crustal plate = a rigid layer of the Earth's crust that is believed to drift slowly
  511. Crux = a small conspicuous constellation in the southern hemisphere in the Milky Way near Centaurus
  512. Crux Australis = a small conspicuous constellation in the southern hemisphere in the Milky Way near Centaurus
  513. crystal = a rock formed by the solidification of a substance; has regularly repeating internal structure
  514. crystallite = any of numerous minute rudimentary crystalline bodies of unknown composition found in glassy igneous rock
  515. crystallization = a rock formed by the solidification of a substance; has regularly repeating internal structure
  516. cultivated land = arable land that is worked by plowing and sowing and raising crops
  517. Cumberland = a river that rises in southeastern Kentucky and flows westward through northern Tennessee to become a tributary of the Ohio River in southwestern Kentucky
  518. Cumberland Gap = a pass through the Cumberland Mountains between Virginia and Kentucky that early settlers used in order to move west
  519. Cumberland Mountains = the southwestern part of the Appalachians
  520. Cumberland Plateau = the southwestern part of the Appalachians
  521. Cumberland River = a river that rises in southeastern Kentucky and flows westward through northern Tennessee to become a tributary of the Ohio River in southwestern Kentucky
  522. cumulonimbus = a dark cloud of great vertical extent charged with electricity
  523. cumulonimbus cloud = a dark cloud of great vertical extent charged with electricity
  524. cumulus = a globular cloud
  525. cumulus cloud = a globular cloud
  526. Cuquenan = a famous waterfall in Venezuela
  527. Cuquenan Falls = a famous waterfall in Venezuela
  528. curtain = any barrier to communication or vision
  529. cutting = a piece cut off from the main part of something
  530. cwm = a steep-walled semicircular basin in a mountain
  531. Cygnus = a constellation in the northern hemisphere between Pegasus and Draco in the Milky Way
  532. cystolith = a calculus formed in the bladder
  533. dale = an open river valley
  534. Danau = the 2nd longest European river
  535. dander = small scales from animal skins or hair or bird feathers that can cause allergic reactions in some people
  536. dandruff = loose scales shed from the scalp
  537. Danube = the 2nd longest European river
  538. Danube River = the 2nd longest European river
  539. Dapsang = a mountain peak in the Karakoram Range in northern Kashmir
  540. Darling = an Australian river
  541. Darling River = an Australian river
  542. Daryacheh-ye Orumiyeh = a shallow saline lake in northwestern Iran between Tabriz and the western border of Turkey
  543. Davy Jones = the bottom of a sea or ocean
  544. Davy Jones's locker = the bottom of a sea or ocean
  545. daystar = a planet (usually Venus) seen just before sunrise in the eastern sky
  546. Dead Sea = a saltwater lake on the border between Israel and Jordan
  547. declension = a downward slope or bend
  548. declination = a downward slope or bend
  549. decline = a downward slope or bend
  550. declivity = a downward slope or bend
  551. deep = literary term for an ocean / a long steep-sided depression in the ocean floor
  552. defile = a narrow pass
  553. Deimos = the outer of two small satellites of Mars
  554. Delaware = a river that rises in the Catskills in southeastern New York and flows southward along the border of Pennsylvania with New York and New Jersey to northern Delaware where it empties into Delaware Bay
  555. Delaware Bay = an inlet of the North Atlantic
  556. Delaware River = a river that rises in the Catskills in southeastern New York and flows southward along the border of Pennsylvania with New York and New Jersey to northern Delaware where it empties into Delaware Bay
  557. dell = a small wooded hollow
  558. Delphinus = a constellation in the northern hemisphere near Pegasus and Aquila
  559. delta = a low triangular area of alluvial deposits where a river divides before entering a larger body of water
  560. delta ray = an electron ejected from matter by ionizing radiation
  561. Demerara = a river in northern Guyana that flows northward into the Atlantic
  562. Denali = a mountain in south central Alaska
  563. Denali Fault = a major open geological fault in Alaska
  564. Deneb = the brightest star in Cygnus
  565. Denebola = a star in Leo approximately 43 light years from Earth
  566. deposit = matter that has been deposited by some natural process
  567. depression = a sunken or depressed geological formation
  568. descent = a downward slope or bend
  569. desideratum = something desired as a necessity
  570. Detroit River = a short river flowing from Lake St. Clair to Lake Erie along the border between the United States and Canada
  571. deuteron = the nucleus of deuterium; consists of one proton and one neutron
  572. Dhaulagiri = a mountain in the Himalayas in Nepal
  573. diapir = a domed rock formation where a core of rock has moved upward and pierced through the more brittle overlying strata
  574. diffuse nebula = a cluster of stars within an intricate cloud of gas and dust
  575. dingle = a small wooded hollow
  576. dipole = a pair of equal and opposite electric charges or magnetic poles separated by a small distance
  577. dipole molecule = a molecule that is a permanent dipole
  578. Dipper = a group of seven bright stars in the constellation Ursa Major / a cluster of seven stars in Ursa Minor
  579. direct transmission = a transmission mechanism in which the infectious agent is transferred directly into the body via touching or biting or kissing or sexual intercourse or by droplets entering the eye or nose or mouth
  580. discard = anything that is cast aside or discarded
  581. distributary = a branch of a river that flows away from the main stream and does not rejoin it
  582. ditch = any small natural waterway
  583. divot = a piece of turf dug out of a lawn or fairway (by an animals hooves or a golf club) / (golf) the cavity left when a piece of turf is cut from the ground by the club head in making a stroke
  584. Dnieper = a river that rises in Russia near Smolensk and flowing south through Belarus and Ukraine to empty into the Black Sea
  585. Dnieper River = a river that rises in Russia near Smolensk and flowing south through Belarus and Ukraine to empty into the Black Sea
  586. dog do = fecal droppings from a dog
  587. dog shit = fecal droppings from a dog
  588. Dog Star = the brightest star in the sky
  589. dog turd = fecal droppings from a dog
  590. doggy do = fecal droppings from a dog
  591. Dolomite Alps = an eastern range of the Alps in northeastern Italy famous for their dolomitic limestone
  592. Don = a European river in southwestern Russia
  593. Don River = a European river in southwestern Russia
  594. Donner Pass = a mountain pass in northeastern California near Lake Tahoe
  595. Dorado = a constellation in the southern hemisphere near Reticulum and Pictor
  596. double star = a system of two stars that revolve around each other under their mutual gravitation
  597. Dove = a constellation in the southern hemisphere near Puppis and Caelum
  598. down = a rolling treeless highland with little soil
  599. down quark = a stable quark with an electric charge of -1/3 and a mass 607 times that of an electron
  600. downhill = the downward slope of a hill
  601. downslope = a downward slope or bend
  602. Draco = a faint constellation twisting around the north celestial pole and lying between Ursa Major and Cepheus
  603. Dragon = a faint constellation twisting around the north celestial pole and lying between Ursa Major and Cepheus
  604. draw = a gully that is shallower than a ravine
  605. dregs = sediment that has settled at the bottom of a liquid
  606. drey = the nest of a squirrel
  607. drift = a large mass of material that is heaped up by the wind or by water currents
  608. drift ice = masses of ice floating in the open sea
  609. drink = any large deep body of water
  610. drop = a steep high face of rock
  611. drop-off = a steep high face of rock
  612. drumlin = a mound of glacial drift
  613. dry land = the solid part of the earth's surface
  614. dry wash = the dry bed of an intermittent stream
  615. dune = a ridge of sand created by the wind
  616. earth = the 3rd planet from the sun
  617. Earth's crust = the outer layer of the Earth
  618. Earth's surface = the outermost level of the land or sea
  619. East China Sea = part of the Pacific Ocean near eastern Asia
  620. East Sea = an arm of the Pacific bordered by Japan, Korea, North Korea, and Russia
  621. East Sear = a tropical arm of the Pacific Ocean near southeastern Asia subject to frequent typhoons
  622. Eastern Highlands = a mountain range running along the eastern coast of Australia
  623. Ebro = a river in northeastern Spain
  624. Ebro River = a river in northeastern Spain
  625. Edgeworth-Kuiper belt = a disk-shaped region of minor planets outside the orbit of Neptune
  626. eggshell = the exterior covering of a bird's egg
  627. El Libertador = a mountain in the Andes in Argentina
  628. El Muerto = a mountain peak in the Andes on the border between Argentina and Chile
  629. Elbe = a river in central Europe that arises in northwestern Czechoslovakia and flows northward through Germany to empty into the North Sea
  630. Elbe River = a river in central Europe that arises in northwestern Czechoslovakia and flows northward through Germany to empty into the North Sea
  631. electric dipole = a dipole with equal and opposite electric charges
  632. electric doublet = a dipole with equal and opposite electric charges
  633. electron = an elementary particle with negative charge
  634. elementary particle = a particle that is less complex than an atom
  635. elevation = a raised or elevated geological formation
  636. eliminator = an agent that eliminates something
  637. Elizabeth River = a short river in southeastern Virginia flowing between Norfolk and Portsmouth into Hampton Roads
  638. embayment = an indentation of a shoreline larger than a cove but smaller than a gulf
  639. ember = a hot fragment of wood or coal that is left from a fire and is glowing or smoldering
  640. enclosure = a naturally enclosed space
  641. encrustation = a hard outer layer that covers something
  642. English Channel = an arm of the Atlantic Ocean that forms a channel between France and Britain
  643. enlivener = an agent that gives or restores life or vigor
  644. enterolith = a calculus occurring in the intestines
  645. envelope = a natural covering
  646. Epsilon Aurigae = the largest known star
  647. Ergun He = a river in eastern Asia that arises in China and flows northeast along the border between China and Russia to become a tributary of the Amur River
  648. Eridanus = a constellation in the southern hemisphere near Fornax and Cetus
  649. Erie = the 4th largest of the Great Lakes
  650. escarpment = a long steep slope or cliff at the edge of a plateau or ridge
  651. esker = a long winding ridge of post glacial gravel and other sediment
  652. essential = anything indispensable
  653. estraterrestrial body = a natural object existing outside the earth and outside the earth's atmosphere
  654. estuary = the wide part of a river where it nears the sea
  655. Euphrates = a river in southwestern Asia; flows into the Persian Gulf
  656. Euphrates River = a river in southwestern Asia; flows into the Persian Gulf
  657. Eurasia = the land mass formed by the continents of Europe and Asia
  658. Europa = the 4th largest of Jupiter's satellites
  659. Europe = the 2nd smallest continent
  660. Euxine Sea = a sea between Europe and Asia
  661. evening star = a planet (usually Venus) seen at sunset in the western sky
  662. Everest = a mountain in the central Himalayas on the border of Tibet and Nepal
  663. Everglades = a large subtropical swamp in southern Florida that is noted for its wildlife
  664. exfoliation = a thin flake of dead epidermis shed from the surface of the skin
  665. existence = everything that exists anywhere
  666. exosphere = the outermost atmospheric layer
  667. expanse = a wide and open space or area as of surface or land or sky
  668. extraterrestrial object = a natural object existing outside the earth and outside the earth's atmosphere
  669. Eyre = a shallow salt lake in south central Australia about 35 feet below sea level
  670. Eyre Peninsula = a peninsula of southern Australia
  671. eyrie = the lofty nest of a bird of prey
  672. eyry = the lofty nest of a bird of prey
  673. faecalith = a hard mass of fecal matter
  674. fall = a downward slope or bend
  675. fallow = cultivated land that is not seeded for one or more growing seasons
  676. falls = a steep descent of the water of a river
  677. farmland = arable land that is worked by plowing and sowing and raising crops
  678. fatigue crack = a crack in metal resulting from metal fatigue
  679. fault = a crack in the earth's crust resulting from the displacement of one side with respect to the other
  680. faulting = a crack in the earth's crust resulting from the displacement of one side with respect to the other
  681. fecalith = a hard mass of fecal matter
  682. feeder = a branch that flows into the main stream
  683. fen = low-lying wet land with grassy vegetation
  684. fenland = low-lying wet land with grassy vegetation
  685. fermion = any particle that obeys Fermi-Dirac statistics and is subject to the Pauli exclusion principle
  686. field = extensive tract of level open land
  687. filing = a fragment rubbed off by the use of a file
  688. finding = something that is found
  689. Fingal's Cave = a large cave with basaltic pillars on Staffa island in Scotland
  690. fiord = a long narrow inlet of the sea between steep cliffs
  691. fire pit = a pit whose floor is incandescent lava
  692. fireball = the luminous center of a nuclear explosion / a ball of fire
  693. firestone = a sandstone that withstands intense heat
  694. firth = a long narrow estuary
  695. Firth of Clyde = a firth on the southwestern coast of Scotland emptying into the North Channel
  696. Firth of Forth = a large firth on the east coast of Scotland and the estuary of the Forth River
  697. fishpond = a freshwater pond with fish
  698. fissure = a long narrow opening
  699. fixed star = any star in the Ptolemaic theory of planetary motion
  700. fjord = a long narrow inlet of the sea between steep cliffs
  701. flake = a small fragment of something broken off from the whole
  702. flare star = a red dwarf star in which luminosity can change several magnitudes in a few minutes
  703. flat = a level tract of land
  704. fleck = a small fragment of something broken off from the whole
  705. Flint = a river in western Georgia that flows generally south to join the Chattahoochee River at the Florida border where they form the Apalachicola River
  706. Flint River = a river in western Georgia that flows generally south to join the Chattahoochee River at the Florida border where they form the Apalachicola River
  707. floater = an object that floats or is capable of floating
  708. floe = a flat mass of ice (smaller than an ice field) floating at sea
  709. flood plain = a low plain adjacent to a river that is formed chiefly of river sediment and is subject to flooding
  710. floodplain = a low plain adjacent to a river that is formed chiefly of river sediment and is subject to flooding
  711. floor = the bottom surface of any lake or other body of water / the ground on which people and animals move about / the lower inside surface of any hollow structure
  712. Florida key = a coral reef off the southern coast of Florida
  713. flowage = a body of water that has been created by deliberately flooding an area
  714. flume = a narrow gorge with a stream running through it
  715. foam = a mass of small bubbles formed in or on a liquid
  716. folium = a thin layer or stratum of (especially metamorphic) rock
  717. fomite = any inanimate object (as a towel or money or clothing or dishes or books or toys etc.) that can transmit infectious agents from one person to another
  718. foothill = a relatively low hill on the lower slope of a mountain
  719. footwall = the lower wall of an inclined fault
  720. ford = a shallow area in a stream that can be forded
  721. foreland = land forming the forward margin of something / a natural elevation
  722. foreshore = the part of the seashore between the highwater mark and the low-water mark
  723. forest = land that is covered with trees and shrubs
  724. formation = the geological features of the earth
  725. formicary = a mound of earth made by ants as they dig their nest
  726. Fornax = a faint constellation in the southern hemisphere near Cetus and Phoenix
  727. Forth = a river in southern Scotland that flows eastward to the Firth of Forth
  728. Forth River = a river in southern Scotland that flows eastward to the Firth of Forth
  729. fossil = the remains (or an impression) of a plant or animal that existed in a past geological age and that has been excavated from the soil
  730. fountain = a natural flow of ground water
  731. Fountain of Youth = a fountain described in folk tales as able to make people young again
  732. Fox River = a river in Wisconsin that flows into Lake Michigan
  733. fracture = a crack in the earth's crust resulting from the displacement of one side with respect to the other
  734. fragment = a piece broken off or cut off of something else
  735. free electron = electron that is not attached to an atom or ion or molecule but is free to move under the influence of an electric field
  736. froth = a mass of small bubbles formed in or on a liquid
  737. full radiator = a hypothetical object capable of absorbing all the electromagnetic radiation falling on it
  738. fundamental particle = a particle that is less complex than an atom
  739. Galan = a mountain peak in the Andes in Argentina
  740. Galilean = one of the four satellites of Jupiter that were discovered by Galileo
  741. Galilean satellite = one of the four satellites of Jupiter that were discovered by Galileo
  742. gallstone = a calculus formed in the gall bladder or its ducts
  743. Galveston Bay = an arm of the Gulf of Mexico in Texas to the south of Houston
  744. Galway Bay = a bay of the North Atlantic on the west coast of Ireland
  745. Gan Jiang = a river in southeastern China that flows generally north into the Chang Jiang to the north of Nanchang
  746. Ganges = an Asian river; rises in the Himalayas and flows east into the Bay of Bengal
  747. Ganges River = an Asian river; rises in the Himalayas and flows east into the Bay of Bengal
  748. Ganymede = the largest of Jupiter's satellites
  749. gap = a pass between mountain peaks / an open or empty space in or between things
  750. Garonne = a river that rises in the Pyrenees and flows northwest to the Bay of Biscay
  751. Garonne River = a river that rises in the Pyrenees and flows northwest to the Bay of Biscay
  752. gas giant = any of the four outermost planets in the solar system
  753. gaseous nebula = a cluster of stars within an intricate cloud of gas and dust
  754. Gasherbrum = a mountain in northern Kashmir
  755. gauge boson = a particle that mediates the interaction of two elementary particles
  756. Gemini = a zodiacal constellation in the northern hemisphere between Taurus and Cancer on the ecliptic
  757. gene delivery vector = a vector for delivering genes into cells
  758. geode = a hollow rock or nodule with the cavity usually lined with crystals
  759. geological fault = a crack in the earth's crust resulting from the displacement of one side with respect to the other
  760. geological formation = the geological features of the earth
  761. geosphere = the solid part of the earth consisting of the crust and outer mantle
  762. geyser = a spring that discharges hot water and steam
  763. giant = a very bright star of large diameter and low density
  764. giant star = a very bright star of large diameter and low density
  765. Gila = a river that rises in western New Mexico and flows westward through southern Arizona to become a tributary of the Colorado River
  766. Gila River = a river that rises in western New Mexico and flows westward through southern Arizona to become a tributary of the Colorado River
  767. glacial boulder = a boulder that has been carried by a glacier to a place far distant from its place of origin
  768. glacier = a slowly moving mass of ice
  769. glen = a narrow secluded valley
  770. globe = the 3rd planet from the sun
  771. globule = a small globe or ball
  772. gluon = a gauge boson that mediates strong interaction among quarks
  773. Godwin Austen = a mountain peak in the Karakoram Range in northern Kashmir
  774. Golden Gate = a strait in western California that connects the San Francisco Bay with the Pacific Ocean
  775. Golfo de Campeche = a part of the Gulf of Mexico to the west of Yucatan
  776. Golfo de Mexico = an arm of the Atlantic to the south of the United States and to the east of Mexico
  777. Gondwanaland = a hypothetical continent that (according to plate tectonic theory) broke up later into India and Australia and Africa and South America and Antarctica
  778. gopher hole = a hole in the ground made by gophers
  779. gorge = a narrow pass (especially one between mountains) / a deep ravine
  780. Gosainthan = a mountain in the Himalayas in Tibet
  781. grain = a relatively small granular particle of a substance
  782. Grand Canyon = the enormous gorge of the Colorado River in northern Arizona
  783. Grand River = a river in southern Michigan that flows northwest to empty into Lake Michigan
  784. Grand Teton = a mountain peak in northwestern Wyoming
  785. granule = a tiny grain
  786. graviton = a gauge boson that mediates the (extremely weak) gravitational interactions between particles
  787. gravity fault = an inclined fault in which the hanging wall appears to have slipped downward relative to the footwall
  788. Great Attractor = a massive grouping of galaxies in the direction of Centaurus and Hydra whose gravitational attraction is believed to cause deviations in the paths of other galaxies
  789. Great Australian Bight = a wide bay of the Indian Ocean in southern Australia
  790. Great Barrier Reef = the largest coral reef in the world
  791. Great Bear = a constellation outside the zodiac that rotates around the North Star
  792. Great Dividing Range = a mountain range running along the eastern coast of Australia
  793. Great Dog = a constellation to the southeast of Orion
  794. Great Lakes = a group of five large, interconnected lakes in central North America
  795. Great Mendenhall Glacier = a glacier of the Piedmont type near Juneau in Alaska
  796. Great Plains = a vast prairie region extending from Alberta and Saskatchewan and Manitoba in Canada south through the west central United States into Texas
  797. Great Plains of North America = a vast prairie region extending from Alberta and Saskatchewan and Manitoba in Canada south through the west central United States into Texas
  798. Great Rift Valley = a depression in southwestern Asia and eastern Africa; extends from the valley of the Jordan River to Mozambique
  799. Great Salt Lake = a shallow body of salt water in northwestern Utah
  800. Great Slave Lake = a lake in the Northwest Territories in northwestern Canada
  801. Great Smoky Mountains = part of the Appalachians between North Carolina and Tennessee
  802. Green = a river that rises in western Wyoming and flows southward through Utah to become a tributary of the Colorado River
  803. Green Mountains = a range of the Appalachian Mountains that extends from south to north through Vermont
  804. Green River = a river that rises in western Wyoming and flows southward through Utah to become a tributary of the Colorado River
  805. Greenland Sea = part of the Arctic Ocean to the north of Iceland
  806. greensward = surface layer of ground containing a mat of grass and grass roots
  807. greenwood = woodlands in full leaf
  808. grinding = material resulting from the process of grinding
  809. grot = a small cave
  810. grotto = a small cave
  811. ground = the solid part of the earth's surface / material in the top layer of the surface of the earth in which plants can grow
  812. grounds = dregs consisting of solid particles (especially of coffee) that form a residue
  813. groundwater level = underground surface below which the ground is wholly saturated with water
  814. growler = a small iceberg or ice floe just large enough to be hazardous for shipping
  815. growth = something grown or growing
  816. Grus = a small constellation in the southern hemisphere near Phoenix
  817. Guadalupe Mountains = a mountain range in southern New Mexico and western Texas
  818. Guaira = a great waterfall on the border between Brazil and Paraguay
  819. Guaira Falls = a great waterfall on the border between Brazil and Paraguay
  820. Guantanamo Bay = an inlet of the Caribbean Sea
  821. guide fossil = a fossil known to have lived in a particular geologic age that can be used to date the rock layer in which it is found
  822. gulch = a narrow gorge with a stream running through it
  823. gulf = a deep wide chasm / an arm of a sea or ocean partly enclosed by land
  824. Gulf Coast = a seashore of the Gulf of Mexico
  825. Gulf of Aden = arm of the Indian Ocean at the entrance to the Red Sea
  826. Gulf of Aegina = a gulf of the Aegean on the southeastern coast of Greece
  827. Gulf of Akaba = a northeastern arm of the Red Sea
  828. Gulf of Alaska = a gulf of the Pacific Ocean between the Alaska Peninsula and the Alexander Archipelago
  829. Gulf of Antalya = a gulf of the Mediterranean Sea in southwestern Turkey
  830. Gulf of Aqaba = a northeastern arm of the Red Sea
  831. Gulf of Bothnia = a northern arm of the Baltic Sea
  832. Gulf of California = a gulf to the west of the mainland of Mexico
  833. Gulf of Campeche = a part of the Gulf of Mexico to the west of Yucatan
  834. Gulf of Carpentaria = a wide shallow inlet of the Arafura Sea in northern Australia
  835. Gulf of Corinth = inlet of the Ionian Sea between central Greece and the Peloponnesus
  836. Gulf of Finland = an eastern arm of the Baltic Sea
  837. Gulf of Guinea = a gulf off the southwest coast of Africa
  838. Gulf of Lepanto = inlet of the Ionian Sea between central Greece and the Peloponnesus
  839. Gulf of Martaban = an arm of the Andaman Sea off southern Myanmar
  840. Gulf of Mexico = an arm of the Atlantic to the south of the United States and to the east of Mexico
  841. Gulf of Ob = an inlet of the Kara Sea in western Siberia
  842. Gulf of Oman = an arm of the Arabian Sea connecting it with the Persian Gulf
  843. Gulf of Riga = an inlet of the Baltic Sea between Latvia and Estonia
  844. Gulf of Saint Lawrence = an arm of the northwest Atlantic Ocean off the southeastern coast of Canada
  845. Gulf of Siam = an arm of the South China Sea between Indochina and the Malay Peninsula
  846. Gulf of Sidra = wide inlet of the Mediterranean Sea on the north coast of Libya
  847. Gulf of St. Lawrence = an arm of the northwest Atlantic Ocean off the southeastern coast of Canada
  848. Gulf of Suez = a northwestern arm of the Red Sea linked to the Mediterranean by the Suez Canal
  849. Gulf of Tehuantepec = an arm of the Pacific in southern Mexico
  850. Gulf of Thailand = an arm of the South China Sea between Indochina and the Malay Peninsula
  851. Gulf of Venice = an arm of the Adriatic Sea
  852. gully = deep ditch cut by running water
  853. gut = a narrow channel or strait
  854. guyot = a seamount of volcanic origin
  855. hadron = any elementary particle that interacts strongly with other particles
  856. hail = many objects thrown forcefully through the air
  857. hair ball = a compact mass of hair that forms in the alimentary canal
  858. hairball = a compact mass of hair that forms in the alimentary canal
  859. hammock = a small natural hill
  860. Hampton Roads = a channel in southeastern Virginia through which the Elizabeth River and the James River flow into Chesapeake Bay
  861. Handies Peak = a mountain peak in the San Juan Mountains in southwestern Colorado
  862. hanging wall = the upper wall of an inclined fault
  863. Hangzhou Bay = a bay formed by an inlet of the East China Sea
  864. head = the foam or froth that accumulates at the top when you pour an effervescent liquid into a container / a rounded compact mass / a natural elevation
  865. headland = a natural elevation
  866. headstream = a stream that forms the source of a river
  867. heavenly body = natural objects visible in the sky
  868. heavy particle = any of the elementary particles having a mass equal to or greater than that of a proton and that participate in strong interactions
  869. Heilong = an Asian river between China and Russia
  870. Heilong Jiang = an Asian river between China and Russia
  871. Hercules = a large constellation in the northern hemisphere between Lyra and Corona Borealis
  872. Hesperus = a planet (usually Venus) seen at sunset in the western sky
  873. heterocycle = a ring of atoms of more than one kind
  874. heterocyclic ring = a ring of atoms of more than one kind
  875. high sea = the open seas of the world outside the territorial waters of any nation
  876. High Sierra = a mountain range in eastern California
  877. highland = elevated (e.g., mountainous) land
  878. hill = a local and well-defined elevation of the land
  879. hillock = a small natural hill
  880. hillside = the side or slope of a hill
  881. Himalaya = a mountain range extending 1500 miles on the border between India and Tibet
  882. Himalaya Mountains = a mountain range extending 1500 miles on the border between India and Tibet
  883. Himalayas = a mountain range extending 1500 miles on the border between India and Tibet
  884. Hindu Kush = a mountain range extending to the west of the Himalayas
  885. Hindu Kush Mountains = a mountain range extending to the west of the Himalayas
  886. hive = a structure that provides a natural habitation for bees
  887. Hoek van Holland = a cape on the southwestern coast of the Netherlands near Rotterdam
  888. hogback = a narrow ridge of hills
  889. hole = an opening into or through something / a depression hollowed out of solid matter
  890. holler = a small valley between mountains
  891. hollow = a depression hollowed out of solid matter / a small valley between mountains
  892. holystone = a soft sandstone used for scrubbing the decks of a ship
  893. honeycomb = a structure of small hexagonal cells constructed from beeswax by bees and used to store honey and larvae
  894. hood = a protective covering that is part of a plant
  895. Hook of Holland = a cape on the southwestern coast of the Netherlands near Rotterdam
  896. hornet's nest = habitation for wasps or hornets
  897. hornets' nest = habitation for wasps or hornets
  898. horseback = a narrow ridge of hills
  899. horsepond = a pond for watering horses
  900. Horseshoe Falls = a part of Niagara Falls in Ontario
  901. horst = a ridge of the earth's crust that has been forced upward between two faults and so is higher than the surrounding land
  902. hot spring = a natural spring of water at a temperature of 70 F or above
  903. Housatonic = a river that rises in western Massachusetts and flows south through Connecticut to empty into Long Island Sound
  904. Housatonic River = a river that rises in western Massachusetts and flows south through Connecticut to empty into Long Island Sound
  905. Huang Hai = part of the Pacific off the east coast of Asia
  906. Huang He = a major river of Asia in northern China; flows generally eastward into the Yellow Sea
  907. Huascaran = a mountain in the Andes in Peru
  908. Hubbard = a mountain peak in southeastern Alaska that is part of the Coast Range
  909. Hudson = a New York river; flows southward into New York Bay
  910. Hudson Bay = an inland sea in northern Canada
  911. Hudson River = a New York river; flows southward into New York Bay
  912. Humber = an estuary in central northeastern England formed by the Ouse River and the Trent River
  913. hummock = a small natural hill
  914. hunk = a large piece of something without definite shape
  915. Hunter = a constellation on the equator to the east of Taurus
  916. Huron = the 2nd largest of the Great Lakes
  917. Hwang Ho = a major river of Asia in northern China; flows generally eastward into the Yellow Sea
  918. Hydra = a long faint constellation in the southern hemisphere near the equator stretching between Virgo and Cancer
  919. hydrogen ion = a positively charged atom of hydrogen
  920. hydrosphere = the watery layer of the earth's surface
  921. Hydrus = a constellation in the southern hemisphere near the south celestial pole
  922. hyperon = any baryon that is not a nucleon
  923. ice = the frozen part of a body of water
  924. ice cap = a mass of ice and snow that permanently covers a large area of land
  925. ice field = a large flat mass of ice (larger than an ice floe) floating at sea
  926. ice floe = a flat mass of ice (smaller than an ice field) floating at sea
  927. ice mass = a large mass of ice
  928. ice pack = a large expanse of floating ice
  929. ice shelf = ice that is attached to land but projects out to sea
  930. iceberg = a large mass of ice floating at sea
  931. icecap = a mass of ice and snow that permanently covers a large area of land
  932. icefall = a steep part of a glacier resembling a frozen waterfall
  933. Iguassu = a large waterfall on the border between Argentina and Brazil
  934. Iguassu Falls = a large waterfall on the border between Argentina and Brazil
  935. Iguazu = a large waterfall on the border between Argentina and Brazil
  936. Iguazu Falls = a large waterfall on the border between Argentina and Brazil
  937. IJssel = a river in the central Netherlands flowing north to the IJsselmeer
  938. IJssel river = a river in the central Netherlands flowing north to the IJsselmeer
  939. IJsselmeer = a shallow lake in northwestern Netherlands created in 1932 by building a dam across the entrance to the Zuider Zee
  940. Illampu = a mountain peak in the Andes in Bolivia
  941. Illimani = a mountain peak in the Andes in Bolivia
  942. Illinois River = a river in Illinois that flows southwest to the Mississippi River
  943. Ilmen = a lake in northwestern Russia
  944. impairer = an agent that impairs
  945. incline = an elevated geological formation
  946. inclined fault = a geological fault in which one side is above the other
  947. inclusion = any small intracellular body found within another
  948. inclusion body = any small intracellular body found within another
  949. incrustation = a hard outer layer that covers something
  950. index fossil = a fossil known to have lived in a particular geologic age that can be used to date the rock layer in which it is found
  951. Indian Ocean = the 3rd largest ocean
  952. Indigirka = a river in far eastern Siberia that flows generally northward to the Arctic Ocean
  953. Indigirka River = a river in far eastern Siberia that flows generally northward to the Arctic Ocean
  954. indirect transmission = a transmission mechanism in which the infectious agent is transferred to the person by a fomite of vector
  955. indument = a covering of fine hairs (or sometimes scales) as on a leaf or insect
  956. indumentum = a covering of fine hairs (or sometimes scales) as on a leaf or insect
  957. Indus = an Asian river that rises in Tibet and flows through northern India and then southwest through Kashmir and Pakistan to the Arabian Sea / a faint constellation in the southern hemisphere near Telescopium and Tucana
  958. Indus River = an Asian river that rises in Tibet and flows through northern India and then southwest through Kashmir and Pakistan to the Arabian Sea
  959. inessential = anything that is not essential
  960. infectious agent = an agent capable of producing infection
  961. infective agent = an agent capable of producing infection
  962. inferior planet = any of the planets whose orbit lies inside the earth's orbit
  963. ingrowth = something that grows inward
  964. Inland Passage = a naturally protected waterway from Seattle to Skagway in southeastern Alaska
  965. Inland Sea = an arm of the Pacific Ocean in southern Japan; surrounded by the islands of Honshu and Shikoku and Kyushu and linked to the Sea of Japan by a narrow channel
  966. inlet = an arm off of a larger body of water
  967. Inside Passage = a naturally protected waterway from Seattle to Skagway in southeastern Alaska
  968. inside track = the inner side of a curved racecourse
  969. intermediate vector boson = a gauge boson that mediates weak interactions between particles
  970. international waters = the open seas of the world outside the territorial waters of any nation
  971. interplanetary dust = microscopic particles in the interplanetary medium
  972. interplanetary gas = a rarefied flow of gas and charged particles (plasma) that stream from the sun and form the solar wind
  973. interplanetary medium = interplanetary space including forms of energy and gas and dust
  974. interstellar medium = interstellar space including streams of protons moving from the stars
  975. intrusion = rock produced by an intrusive process
  976. invigorator = an agent that gives or restores life or vigor
  977. Io = the closest of Jupiter's moons
  978. ion = a particle that is electrically charged
  979. Ionian Sea = an arm of the Mediterranean Sea between western Greece and southern Italy
  980. Irish Sea = an arm of the North Atlantic between Great Britain and Ireland
  981. iron filing = a fragment of iron rubbed off by the use of a file
  982. Irrawaddy = the main river of Myanmar rising in the north and flowing south through the length of Burma to empty into the Andaman Sea
  983. Irrawaddy River = the main river of Myanmar rising in the north and flowing south through the length of Burma to empty into the Andaman Sea
  984. Irtish = an Asian river that rises in the Altai Mountains in northern China and flows generally northwest to become a tributary of the Ob River
  985. Irtish River = an Asian river that rises in the Altai Mountains in northern China and flows generally northwest to become a tributary of the Ob River
  986. Irtysh = an Asian river that rises in the Altai Mountains in northern China and flows generally northwest to become a tributary of the Ob River
  987. Irtysh River = an Asian river that rises in the Altai Mountains in northern China and flows generally northwest to become a tributary of the Ob River
  988. Isere = a river in southeastern France
  989. Isere River = a river in southeastern France
  990. island = a land mass (smaller than a continent) that is surrounded by water
  991. isle = a small island
  992. Isle of Wight = an isle and county of southern England in the English Channel
  993. islet = a small island
  994. isthmus = a relatively narrow strip of land (with water on both sides) connecting two larger land areas
  995. Isthmus of Corinth = a narrow isthmus between the Gulf of Corinth and the Saronic Gulf
  996. Isthmus of Darien = the isthmus that connects Central America and South America
  997. Isthmus of Kra = a narrow isthmus linking the Malay Peninsula to the Asian mainland
  998. Isthmus of Panama = the isthmus that connects Central America and South America
  999. Isthmus of Suez = the isthmus in northeastern Egypt that connects Africa and Asia
  1000. Isthmus of Tehuantepec = the narrowest part of southern Mexico is an isthmus between the Bay of Campeche on the north coast and the Gulf of Tehuantepec on the south coast
  1001. J particle = a neutral meson with a large mass
  1002. jag = a sharp projection on an edge or surface
  1003. James = a river that rises in North Dakota and flows southward across South Dakota to the Missouri / a river in Virginia that flows east into Chesapeake Bay at Hampton Roads
  1004. James Bay = the southern extension of Hudson Bay in Canada between western Quebec and northeastern Ontario
  1005. James River = a river that rises in North Dakota and flows southward across South Dakota to the Missouri / a river in Virginia that flows east into Chesapeake Bay at Hampton Roads
  1006. Japan Trench = a depression in the floor of the Pacific Ocean to the northeast of Japan that reaches depths of 30,000 feet
  1007. Jebel Musa = a promontory in northern Morocco opposite the Rock of Gibraltar
  1008. Jordan = a river in Palestine that empties into the Dead Sea
  1009. Jordan River = a river in Palestine that empties into the Dead Sea
  1010. Jovian planet = any of the four outermost planets in the solar system
  1011. Jupiter = the largest planet and the 5th from the sun
  1012. K particle = an unstable meson produced as the result of a high-energy particle collision
  1013. k-meson = an unstable meson produced as the result of a high-energy particle collision
  1014. K2 = a mountain peak in the Karakoram Range in northern Kashmir
  1015. Kamet = a mountain in the Himalayas in northern India
  1016. Kan River = a river in southeastern China that flows generally north into the Chang Jiang to the north of Nanchang
  1017. Kanawha = a tributary of the Ohio River in West Virginia
  1018. Kanawha River = a tributary of the Ohio River in West Virginia
  1019. Kanchanjanga = a mountain the Himalayas on the border between Nepal and Tibet
  1020. Kanchenjunga = a mountain the Himalayas on the border between Nepal and Tibet
  1021. Kansas = a river in northeastern Kansas
  1022. Kansas River = a river in northeastern Kansas
  1023. kaon = an unstable meson produced as the result of a high-energy particle collision
  1024. kappa-meson = an unstable meson produced as the result of a high-energy particle collision
  1025. Kara Sea = part of the Arctic Ocean to the north of Siberia and to the east of the Barents Sea
  1026. Karakoram = a mountain range in northern Kashmir; an extension of the Hindu Kush
  1027. Karakoram Range = a mountain range in northern Kashmir; an extension of the Hindu Kush
  1028. Karakorum Range = a mountain range in northern Kashmir; an extension of the Hindu Kush
  1029. Karelian Isthmus = the isthmus between the Gulf of Finland and Lake Ladoga that connects Finland and Russia
  1030. Kasai = a river of southwestern Africa that rises in central Angola and flows east and then north (forming part of the border between Angola and Congo) and continuing northwest through Congo to empty into the Congo River on the border between Congo and Republic of the Congo
  1031. Kasai River = a river of southwestern Africa that rises in central Angola and flows east and then north (forming part of the border between Angola and Congo) and continuing northwest through Congo to empty into the Congo River on the border between Congo and Republic of the Congo
  1032. Kattegatt = a strait of the North Sea between Jutland and Sweden
  1033. Kaw River = a river in northeastern Kansas
  1034. KBO = any of many minor planets in the Kuiper belt outside the orbit of Neptune at the edge of the solar system
  1035. kettle = a hollow (typically filled by a lake) that results from the melting of a mass of ice trapped in glacial deposits
  1036. kettle hole = a hollow (typically filled by a lake) that results from the melting of a mass of ice trapped in glacial deposits
  1037. Keuka Lake = a glacial lake in central New York
  1038. key = a coral reef off the southern coast of Florida
  1039. Khyber Pass = a mountain pass of great strategic and commercial value in the Hindu Kush on the border between northern Pakistan and western Afghanistan
  1040. kidney stone = a calculus formed in the kidney
  1041. Kilimanjaro = the highest peak in Africa; located in northeastern Tanzania
  1042. Kinchinjunga = a mountain the Himalayas on the border between Nepal and Tibet
  1043. Kissimmee = a river of central Florida that flows southward to Lake Okeechobee
  1044. Kissimmee River = a river of central Florida that flows southward to Lake Okeechobee
  1045. Kivu = a lake in the mountains of central Africa between Congo and Rwanda
  1046. Klamath = a river flowing southwest from Oregon through northern California to the Pacific Ocean
  1047. Klamath River = a river flowing southwest from Oregon through northern California to the Pacific Ocean
  1048. knoll = a small natural hill
  1049. Kodiak = an island off southern Alaska in the Gulf of Alaska
  1050. Kodiak Island = an island off southern Alaska in the Gulf of Alaska
  1051. kopje = a small hill rising up from the African veld
  1052. koppie = a small hill rising up from the African veld
  1053. Korea Bay = an inlet of the Yellow Sea between the Liaodong Peninsula in China and western Korea
  1054. Korea Strait = a strait between Korea and Japan
  1055. Korean Strait = a strait between Korea and Japan
  1056. Kuenlun = a mountain range in western China that extends eastward from the Indian border for 1000 miles
  1057. Kuenlun Mountains = a mountain range in western China that extends eastward from the Indian border for 1000 miles
  1058. Kuiper belt = a disk-shaped region of minor planets outside the orbit of Neptune
  1059. Kuiper belt object = any of many minor planets in the Kuiper belt outside the orbit of Neptune at the edge of the solar system
  1060. Kukenaam = a famous waterfall in Venezuela
  1061. Kukenaam Falls = a famous waterfall in Venezuela
  1062. Kunlan Shan = a mountain range in western China that extends eastward from the Indian border for 1000 miles
  1063. Kunlun = a mountain range in western China that extends eastward from the Indian border for 1000 miles
  1064. Kunlun Mountains = a mountain range in western China that extends eastward from the Indian border for 1000 miles
  1065. Kura = a river in western Asia
  1066. Kura River = a river in western Asia
  1067. La Plata = an estuary between Argentina and Uruguay
  1068. Labrador Peninsula = a peninsular region of eastern Canada between Hudson Bay and the Labrador Sea
  1069. Labrador Sea = an arm of the northern Atlantic between Labrador and southern Greenland
  1070. Labrador-Ungava Peninsula = a peninsular region of eastern Canada between Hudson Bay and the Labrador Sea
  1071. Ladoga = a lake in northwestern Russia to the north of St. Petersburg; the largest lake in Europe
  1072. lagoon = a body of water cut off from a larger body by a reef of sand or coral
  1073. laguna = a body of water cut off from a larger body by a reef of sand or coral
  1074. lagune = a body of water cut off from a larger body by a reef of sand or coral
  1075. lake = a body of (usually fresh) water surrounded by land
  1076. Lake Albert = a shallow lake on the border between Uganda and Congo in the Great Rift Valley
  1077. Lake Albert Nyanza = a shallow lake on the border between Uganda and Congo in the Great Rift Valley
  1078. Lake Aral = a lake to the east of the Caspian Sea lying between Kazakhstan and Uzbekistan
  1079. Lake Baikal = the largest freshwater lake in Asia or Europe and the deepest lake in the world
  1080. Lake Balaton = a large shallow lake in western Hungary
  1081. Lake Baykal = the largest freshwater lake in Asia or Europe and the deepest lake in the world
  1082. lake bed = the bottom of a lake
  1083. lake bottom = the bottom of a lake
  1084. Lake Canandaigua = a glacial lake in central New York
  1085. Lake Cayuga = a glacial lake in central New York
  1086. Lake Chad = a lake in north central Africa
  1087. Lake Champlain = a lake in northeastern New York, northwestern Vermont and southern Quebec
  1088. Lake Chelan = a narrow very deep lake in central Washington in the Cascade Range
  1089. Lake Constance = a lake in southeastern Germany on the northern side of the Swiss Alps
  1090. Lake Edward = a lake in the Great Rift Valley between Congo and Uganda
  1091. Lake Erie = the 4th largest of the Great Lakes
  1092. Lake Eyre = a shallow salt lake in south central Australia about 35 feet below sea level
  1093. Lake Geneva = a lake between southwestern Switzerland and France that is crossed from east to west by the Rhone
  1094. Lake Huron = the 2nd largest of the Great Lakes
  1095. Lake Ilmen = a lake in northwestern Russia
  1096. Lake Keuka = a glacial lake in central New York
  1097. Lake Kivu = a lake in the mountains of central Africa between Congo and Rwanda
  1098. Lake Ladoga = a lake in northwestern Russia to the north of St. Petersburg; the largest lake in Europe
  1099. Lake Leman = a lake between southwestern Switzerland and France that is crossed from east to west by the Rhone
  1100. Lake Malawi = a long lake in southeastern Africa between Tanzania, Mozambique, and Malawi
  1101. Lake Michigan = the 3rd largest of the Great Lakes
  1102. Lake Nasser = lake in Egypt formed by dams built on the Nile River at Aswan
  1103. Lake Nyasa = a long lake in southeastern Africa between Tanzania, Mozambique, and Malawi
  1104. Lake Okeechobee = a lake in southeast Florida to the north of the Everglades
  1105. Lake Onega = lake in northwestern Russia near the border with Finland
  1106. Lake Ontario = the smallest of the Great Lakes
  1107. Lake Saint Clair = a lake between Ontario and Michigan
  1108. Lake Seneca = a glacial lake in central New York
  1109. Lake St. Clair = a lake between Ontario and Michigan
  1110. Lake Superior = the largest freshwater lake in the world
  1111. Lake Tahoe = a lake on the border between Nevada and California to the west of Carson City
  1112. Lake Tana = a lake in northern Ethiopia
  1113. Lake Tanganyika = the longest lake in the world in central Africa between Tanzania and Congo in the Great Rift Valley
  1114. Lake Tsana = a lake in northern Ethiopia
  1115. Lake Urmia = a shallow saline lake in northwestern Iran between Tabriz and the western border of Turkey
  1116. Lake Vanern = a lake in southwestern Sweden
  1117. Lake Victoria = the largest lake in Africa and the 2nd largest fresh water lake in the world
  1118. Lake Winnipeg = a lake in southern Canada in Manitoba
  1119. lakefront = land bordering a lake
  1120. lakeshore = the shore of a lake
  1121. lakeside = the shore of a lake
  1122. lambda hyperon = an electrically neutral baryon with isotopic spin 1
  1123. lambda particle = an electrically neutral baryon with isotopic spin 1
  1124. land = the solid part of the earth's surface / material in the top layer of the surface of the earth in which plants can grow
  1125. land mass = a large continuous extent of land
  1126. landfall = the seacoast first sighted on a voyage
  1127. landfill = a low area that has been filled in
  1128. landmass = a large continuous extent of land
  1129. Laptev Sea = part of the Arctic Ocean to the north of Siberia (between the Taimyr Peninsula and the New Siberian Islands) that is icebound most of the year
  1130. Large Magellanic Cloud = the larger of the two Magellanic Clouds visible from the southern hemisphere
  1131. Lascaux = a cave in southwestern France that contains Paleolithic paintings
  1132. lather = the foam resulting from excessive sweating (as on a horse) / the froth produced by soaps or detergents
  1133. Laudo = a mountain peak in the Andes in Argentina
  1134. Laurasia = a hypothetical continent that (according to plate tectonic theory) broke up later into North America and Europe and Asia
  1135. leak = an accidental hole that allows something (fluid or light etc.) to enter or escape
  1136. ledge = a projecting ridge on a mountain or submerged under water
  1137. lees = the sediment from fermentation of an alcoholic beverage
  1138. Lehigh River = a river in eastern Pennsylvania that flows southeast into the Delaware River
  1139. Lena = a Russian river in Siberia
  1140. Lena River = a Russian river in Siberia
  1141. Leo = a zodiacal constellation in northern hemisphere between Cancer and Virgo
  1142. lepton = an elementary particle that participates in weak interactions
  1143. Lepus = a constellation in the southern hemisphere near Orion and Columba
  1144. lethal agent = an agent capable of causing death
  1145. Lethe = a river in Hades
  1146. Lhotse = a mountain in the central Himalayas on the border of Tibet and Nepal
  1147. Liakoura = a mountain in central Greece where (according to Greek mythology) the Muses lived
  1148. Liaodong Bandao = a peninsula in northeastern China that extends into the Yellow Sea, between Bo Hai and Korea Bay
  1149. Liaodong Peninsula = a peninsula in northeastern China that extends into the Yellow Sea, between Bo Hai and Korea Bay
  1150. Libra = a small faint zodiacal constellation in the southern hemisphere
  1151. lick = a salt deposit that animals regularly lick
  1152. Ligurian Sea = an arm of the Mediterranean between northwest Italy and Corsica
  1153. liman = a long narrow lagoon near the mouth of a river
  1154. Limpopo = an African river
  1155. liposomal delivery vector = a transducing vector that uses liposomes to carry the gene of interest
  1156. lithosphere = the solid part of the earth consisting of the crust and outer mantle
  1157. Little Bear = a constellation outside the zodiac that rotates around the North Star
  1158. Little Bighorn = a river that flows from northern Wyoming into the Bighorn River in southern Montana
  1159. Little Bighorn River = a river that flows from northern Wyoming into the Bighorn River in southern Montana
  1160. Little Dipper = a cluster of seven stars in Ursa Minor
  1161. Little Dog = a constellation to the east of Orion
  1162. Little Horn = a river that flows from northern Wyoming into the Bighorn River in southern Montana
  1163. Little Missouri = a river that rises in northeastern Wyoming and flows through Montana and South Dakota to join the Missouri River in North Dakota
  1164. Little Missouri River = a river that rises in northeastern Wyoming and flows through Montana and South Dakota to join the Missouri River in North Dakota
  1165. Little Sioux River = a river that rises in southwestern Minnesota and flows southwestward to the Missouri River in western Iowa
  1166. Little Wabash = a river in eastern Illinois that flows southeastward to the Wabash River
  1167. Little Wabash River = a river in eastern Illinois that flows southeastward to the Wabash River
  1168. llano = an extensive grassy and nearly treeless plain
  1169. Llano Estacado = a large semiarid plateau forming the southern part of the Great Plains
  1170. Llullaillaco = a mountain in the Andes on the border between Argentina and Chile
  1171. loadstar = guiding star
  1172. loch = Scottish word for a lake / a long narrow inlet of the sea in Scotland
  1173. Loch Achray = a lake in central Scotland
  1174. Loch Linnhe = an inlet of the Atlantic Ocean on the western coast of Scotland
  1175. Loch Ness = a lake in the Scottish highlands
  1176. lodestar = guiding star
  1177. Logan = a mountain peak in the St. Elias Range in the southwestern Yukon Territory in Canada
  1178. Loire = the longest French river
  1179. Loire River = the longest French river
  1180. Loire Valley = the valley of the Loire River where many French wines originated
  1181. long chain = a relatively long chain of atoms in a molecule
  1182. Long Island Sound = a sound between Long Island and Connecticut
  1183. long-chain molecule = a relatively long chain of atoms in a molecule
  1184. lough = Irish word for a lake / a long narrow (nearly landlocked) cove in Ireland
  1185. Lower California = a mountainous peninsula on northwest Mexico
  1186. lower mantle = the deeper part of the mantle
  1187. Lower Peninsula = the part of Michigan between Lake Michigan and Lake Huron
  1188. Lower Tunguska = a river that arises to the north of Lake Baikal and flows north and west to the Yenisei River
  1189. lowland = low level country
  1190. Lucifer = a planet (usually Venus) seen just before sunrise in the eastern sky
  1191. lump = a large piece of something without definite shape
  1192. lunar crater = a crater on the Earth's Moon
  1193. Lupus = a constellation in the southern hemisphere near Centaurus
  1194. Lyra = a small constellation in the northern hemisphere near Cygnus and Draco
  1195. maar = a flat-bottomed volcanic crater that was formed by an explosion
  1196. Mackenzie = a Canadian river
  1197. Mackenzie River = a Canadian river
  1198. mackerel sky = a sky filled with rows of cirrocumulus or small altocumulus clouds
  1199. macrocosm = everything that exists anywhere
  1200. Madeira = a Brazilian river
  1201. Madeira River = a Brazilian river
  1202. Magdalena = a river that rises in the Andes mountains in southwestern Colombia and flows generally northward to empty into the Caribbean Sea at Barranquilla
  1203. Magdalena River = a river that rises in the Andes mountains in southwestern Colombia and flows generally northward to empty into the Caribbean Sea at Barranquilla
  1204. Magellanic Cloud = either of two small galaxies orbiting the Milky Way
  1205. magnetic dipole = a dipole with opposing magnetic poles
  1206. magnetic monopole = a hypothetical particle with a single magnetic pole instead of the usual two
  1207. main = any very large body of (salt) water
  1208. mainland = the main land mass of a country or continent
  1209. major planet = any of the nine large celestial bodies in the solar system that revolve around the sun and shine by reflected light; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto in order of their proximity to the sun
  1210. Makalu = a mountain in the Himalayas in Nepal
  1211. mantle = anything that covers / the layer of the earth between the crust and the core
  1212. mare = a dark region of considerable extent on the surface of the moon
  1213. mare clausum = a navigable body of water under the jurisdiction of a single nation
  1214. mare liberum = a navigable body of water to which all nations have equal access
  1215. mare nostrum = the Mediterranean to the ancient Romans
  1216. mare's tail = a long narrow flowing cirrus cloud
  1217. maria = a dark region of considerable extent on the surface of the moon
  1218. Marmara = an inland sea in northwestern Turkey
  1219. Marmara Denizi = an inland sea in northwestern Turkey
  1220. Marmora = an inland sea in northwestern Turkey
  1221. Mars = a small reddish planet that is the 4th from the sun and is periodically visible to the naked eye
  1222. marsh = low-lying wet land with grassy vegetation
  1223. marshland = low-lying wet land with grassy vegetation
  1224. mass = a body of matter without definite shape
  1225. Massachusetts Bay = an inlet of the Atlantic Ocean off of eastern Massachusetts extending from Cape Ann on the north to Cape Cod on the south
  1226. massif = a block of the earth's crust bounded by faults and shifted to form peaks of a mountain range
  1227. Massif Central = a mountainous plateau in southern France that covers almost one sixth of the country
  1228. mat = a mass that is densely tangled or interwoven
  1229. matchwood = fragments of wood
  1230. matrix = an enclosure within which something originates or develops
  1231. Matterhorn = a mountain in the Alps on the border between Switzerland and Italy
  1232. McKinley = a mountain in south central Alaska
  1233. meander = a bend or curve, as in a stream or river
  1234. mechanism = a natural object resembling a machine in structure or function
  1235. Mediterranean = the largest inland sea
  1236. Mediterranean Sea = the largest inland sea
  1237. Mekong = an Asian river
  1238. Mekong River = an Asian river
  1239. Menai Strait = a strait in northern Wales between Anglesey Island and the mainland
  1240. Mendenhall Glacier = a glacier of the Piedmont type near Juneau in Alaska
  1241. Mensa = a faint constellation in the polar region of the southern hemisphere and containing part of the Large Magellanic Cloud
  1242. Mercedario = a mountain in the Andes in Argentina
  1243. Mercury = the smallest planet and the nearest to the sun
  1244. mere = a small pond of standing water
  1245. Merrimack = a river that rises in south central New Hampshire and flows through Concord and Manchester into Massachusetts and empties into the Atlantic Ocean
  1246. Merrimack River = a river that rises in south central New Hampshire and flows through Concord and Manchester into Massachusetts and empties into the Atlantic Ocean
  1247. mesa = flat tableland with steep edges
  1248. Mesabi Range = a range of hills in northeastern Minnesota where rich iron ore deposits were discovered in 1887
  1249. meson = an elementary particle responsible for the forces in the atomic nucleus
  1250. mesosphere = the atmospheric layer between the stratosphere and the thermosphere
  1251. mesotron = an elementary particle responsible for the forces in the atomic nucleus
  1252. metal filing = a fragment of metal rubbed off by the use of a file
  1253. meteor = any of the small solid extraterrestrial bodies that hits the earth's atmosphere
  1254. meteor swarm = a group of meteoroids with similar paths
  1255. meteorite = stony or metallic object that is the remains of a meteoroid that has reached the earth's surface
  1256. meteoroid = any of the small solid extraterrestrial bodies that hits the earth's atmosphere
  1257. Meuse = a European river
  1258. Meuse River = a European river
  1259. micelle = an electrically charged particle built up from polymeric molecules or ions and occurring in certain colloidal electrolytic solutions like soaps and detergents
  1260. Michigan = the 3rd largest of the Great Lakes
  1261. microfossil = a fossil that must be studied microscopically
  1262. micrometeor = a meteorite or meteoroid so small that it drifts down to earth without becoming intensely heated in the atmosphere
  1263. micrometeorite = a meteorite or meteoroid so small that it drifts down to earth without becoming intensely heated in the atmosphere
  1264. micrometeoroid = a meteorite or meteoroid so small that it drifts down to earth without becoming intensely heated in the atmosphere
  1265. Microscopium = a faint constellation in the southern hemisphere near Sagittarius and Capricornus
  1266. Mid-Atlantic Ridge = a very long narrow elevation on the ocean floor that runs all the way from Iceland in the North Atlantic to Bouvet Island in the South Atlantic
  1267. mid-water = the water that is well below the surface but also well above the bottom
  1268. midstream = the middle of a stream
  1269. Milk = a river that rises in the Rockies in northwestern Montana and flows eastward to become a tributary of the Missouri River
  1270. Milk River = a river that rises in the Rockies in northwestern Montana and flows eastward to become a tributary of the Missouri River
  1271. Milky Way = the galaxy containing the solar system
  1272. Milky Way Galaxy = the galaxy containing the solar system
  1273. Milky Way System = the galaxy containing the solar system
  1274. millpond = a pond formed by damming a stream to provide a head of water to turn a mill wheel
  1275. Minamata Bay = a bay on the west coast of Kyushu
  1276. mineral vein = a layer of ore between layers of rock
  1277. minor planet = any of numerous small celestial bodies that move around the sun
  1278. mire = a soft wet area of low-lying land that sinks underfoot
  1279. Mississippi = a major North American river and the chief river of the United States
  1280. Mississippi River = a major North American river and the chief river of the United States
  1281. Missouri = the longest river in the United States
  1282. Missouri River = the longest river in the United States
  1283. Mobile = a river in southwestern Alabama
  1284. Mobile Bay = a bay of the Gulf of Mexico
  1285. Mobile River = a river in southwestern Alabama
  1286. Mobuto Lake = a shallow lake on the border between Uganda and Congo in the Great Rift Valley
  1287. Mohawk River = a river of central New York that flows southeastward to the Hudson River
  1288. Moho = the boundary between the Earth's crust and the underlying mantle
  1289. Mohorovicic discontinuity = the boundary between the Earth's crust and the underlying mantle
  1290. molehill = a mound of earth made by moles while burrowing
  1291. monocline = a geological formation in which all strata are inclined in the same direction
  1292. Monongahela = a river that rises in northern West Virginia and flows north into Pennsylvania where it joins the Allegheny River at Pittsburgh to form the Ohio River
  1293. Monongahela River = a river that rises in northern West Virginia and flows north into Pennsylvania where it joins the Allegheny River at Pittsburgh to form the Ohio River
  1294. Mont Blanc = the highest mountain peak in the Alps
  1295. Monte Bianco = the highest mountain peak in the Alps
  1296. Monterey Bay = an inlet of the Pacific Ocean in western California
  1297. moon = any natural satellite of a planet / the natural satellite of the Earth / any object resembling a moon
  1298. moor = open land usually with peaty soil covered with heather and bracken and moss
  1299. moorland = open land usually with peaty soil covered with heather and bracken and moss
  1300. moraine = accumulated earth and stones deposited by a glacier
  1301. morass = a soft wet area of low-lying land that sinks underfoot
  1302. Moray Firth = an inlet of the North Sea on the northeast coast of Scotland
  1303. Moreau River = a river that rises in western South Dakota and flows eastward to the Missouri River
  1304. Moreton Bay = an arm of the Tasman Sea forming a bay to the east of Brisbane
  1305. morning star = a planet (usually Venus) seen just before sunrise in the eastern sky
  1306. mother-of-pearl cloud = a luminous iridescent cloud at a high altitude that may be seen when the sun is a few degrees below the horizon
  1307. motor = a nonspecific agent that imparts motion
  1308. mound = a small natural hill
  1309. mount = a land mass that projects well above its surroundings
  1310. Mount Adams = a mountain peak in southwestern Washington in the Cascade Range
  1311. Mount Ararat = the mountain peak that Noah's ark landed on as the waters of the great flood receded
  1312. Mount Bartle Frere = the highest mountain peak in Queensland, Australia
  1313. Mount Carmel = a mountain range in northwestern Israel near the Mediterranean coast
  1314. Mount Communism = the highest mountain peak in the Pamir Mountains
  1315. Mount Elbert = the highest peak in the Rocky Mountains in central Colorado
  1316. Mount Everest = a mountain in the central Himalayas on the border of Tibet and Nepal
  1317. Mount Garmo = the highest mountain peak in the Pamir Mountains
  1318. Mount Godwin Austen = a mountain peak in the Karakoram Range in northern Kashmir
  1319. Mount Hubbard = a mountain peak in southeastern Alaska that is part of the Coast Range
  1320. Mount Kanchenjunga = a mountain the Himalayas on the border between Nepal and Tibet
  1321. Mount Kilimanjaro = the highest peak in Africa; located in northeastern Tanzania
  1322. Mount Logan = a mountain peak in the St. Elias Range in the southwestern Yukon Territory in Canada
  1323. Mount McKinley = a mountain in south central Alaska
  1324. Mount Olympus = a mountain peak in northeast Greece near the Aegean coast
  1325. Mount Parnassus = a mountain in central Greece where (according to Greek mythology) the Muses lived
  1326. Mount Rainier = a mountain peak in central Washington; highest peak in the Cascade Range
  1327. Mount Rushmore = a mountain in the Black Hills of South Dakota
  1328. Mount Shasta = a volcanic mountain peak in the Cascade Range in northern California
  1329. Mount Sherman = a peak in the Rocky Mountains in central Colorado
  1330. Mount Sinai = a mountain peak in the southern Sinai Peninsula
  1331. Mount Tacoma = a mountain peak in central Washington; highest peak in the Cascade Range
  1332. Mount Whitney = the highest peak in the Sierra Nevada range in California
  1333. Mount Wilson = a peak in the San Juan mountains of Colorado
  1334. mountain = a land mass that projects well above its surroundings
  1335. mountain chain = a series of hills or mountains
  1336. mountain pass = the location in a range of mountains of a geological formation that is lower than the surrounding peaks
  1337. mountain peak = the summit of a mountain
  1338. mountain range = a series of hills or mountains
  1339. mountainside = the side or slope of a mountain
  1340. mouse nest = where mice bear and raise their young
  1341. mouse's nest = where mice bear and raise their young
  1342. mouth = the point where a stream issues into a larger body of water / an opening that resembles a mouth
  1343. Mozambique Channel = an arm of the Indian Ocean between Madagascar and southeastern Africa
  1344. Mt. Ararat = the mountain peak that Noah's ark landed on as the waters of the great flood receded
  1345. Mt. Everest = a mountain in the central Himalayas on the border of Tibet and Nepal
  1346. Mt. McKinley = a mountain in south central Alaska
  1347. Mt. Olympus = a mountain peak in northeast Greece near the Aegean coast
  1348. Mt. Rainier = a mountain peak in central Washington; highest peak in the Cascade Range
  1349. Mt. Rushmore = a mountain in the Black Hills of South Dakota
  1350. mu-meson = an elementary particle with a negative charge and a half-life of 2 microsecond
  1351. mud puddle = a puddle of mud
  1352. mull = a term used in Scottish names of promontories
  1353. multiple star = a system of three or more stars associated by gravity
  1354. muon = an elementary particle with a negative charge and a half-life of 2 microsecond
  1355. Murray = a southeast Australian river
  1356. Murray River = a southeast Australian river
  1357. Murrumbidgee = a river of southeastern Australia
  1358. Murrumbidgee River = a river of southeastern Australia
  1359. Musca = a small constellation in the polar region of the southern hemisphere near the Southern Cross and Chamaeleon
  1360. mush = any soft or soggy mass
  1361. must = a necessary or essential thing
  1362. Mustagh = a mountain range in northern Kashmir; an extension of the Hindu Kush
  1363. Mustagh Range = a mountain range in northern Kashmir; an extension of the Hindu Kush
  1364. mutagen = any agent (physical or environmental) that can induce a genetic mutation or can increase the rate of mutation
  1365. Muztag = a highest mountain peak in the Kunlun Shan in China
  1366. Muztagh = a highest mountain peak in the Kunlun Shan in China
  1367. Nacimiento = a mountain peak in the Andes in Argentina
  1368. nacreous cloud = a luminous iridescent cloud at a high altitude that may be seen when the sun is a few degrees below the horizon
  1369. Namoi = a river in southeastern Australia that flows generally northwest to join the Darling River
  1370. Namoi River = a river in southeastern Australia that flows generally northwest to join the Darling River
  1371. Nan = a river of western Thailand flowing southward to join the Ping River to form the Chao Phraya
  1372. Nan Ling = a mountain range in southeastern China running generally east to west
  1373. Nan River = a river of western Thailand flowing southward to join the Ping River to form the Chao Phraya
  1374. Nanda Devi = a mountain in the Himalayas in northern India
  1375. Nanga Parbat = a mountain in the Himalayas in Kashmir
  1376. Nares Deep = a depression in the floor of the Atlantic Ocean to the north of Haiti and Puerto Rico
  1377. Narragansett Bay = a deep inlet of the Atlantic Ocean in Rhode Island
  1378. narrow = a narrow strait connecting two bodies of water
  1379. Nasser = lake in Egypt formed by dams built on the Nile River at Aswan
  1380. natural covering = a natural object that covers or envelops
  1381. natural depression = a sunken or depressed geological formation
  1382. natural elevation = a raised or elevated geological formation
  1383. natural enclosure = a naturally enclosed space
  1384. natural order = the physical universe considered as an orderly system subject to natural (not human or supernatural) laws
  1385. natural spring = a natural flow of ground water
  1386. nature = the natural physical world including plants and animals and landscapes etc.
  1387. nebula = an immense cloud of gas (mainly hydrogen) and dust in interstellar space
  1388. nebule = a small cloud
  1389. necessary = anything indispensable
  1390. necessity = anything indispensable
  1391. neck = a narrow elongated projecting strip of land
  1392. Neckar = a river in Germany
  1393. Neckar River = a river in Germany
  1394. need = anything that is necessary but lacking
  1395. negative muon = an elementary particle with a negative charge and a half-life of 2 microsecond
  1396. negatron = an elementary particle with negative charge
  1397. neighbor = a nearby object of the same kind
  1398. neighbour = a nearby object of the same kind
  1399. Neosho = a river that rises in eastern Kansas and flows eastward into Oklahoma to become a tributary of the Arkansas River
  1400. Neosho River = a river that rises in eastern Kansas and flows eastward into Oklahoma to become a tributary of the Arkansas River
  1401. nephrolith = a calculus formed in the kidney
  1402. Neptune = a giant planet with a ring of ice particles
  1403. neritic zone = the ocean waters from the low tide mark to a depth of about 100 fathoms
  1404. ness = a strip of land projecting into a body of water
  1405. nest = a structure in which animals lay eggs or give birth to their young
  1406. neutrino = an elementary, electrically neutral particle with a very small mass
  1407. neutron = an elementary particle with 0 charge and mass about equal to a proton
  1408. neutron star = a star that has collapsed under its own gravity
  1409. Neva = a river in northwestern Russia flowing generally west into the Gulf of Finland
  1410. Neva River = a river in northwestern Russia flowing generally west into the Gulf of Finland
  1411. neve = the upper part of a glacier (beyond the limit of perpetual snow) where the snow turns to ice
  1412. New River = a river in the southeastern United States that flows northward from North Carolina to West Virginia where it empties into the Kanawha River
  1413. New York Bay = a bay of the North Atlantic
  1414. Niagara = a river flowing from Lake Erie into Lake Ontario; forms boundary between Ontario and New York / waterfall in Canada is the Horseshoe Falls
  1415. Niagara Falls = waterfall in Canada is the Horseshoe Falls
  1416. Niagara River = a river flowing from Lake Erie into Lake Ontario
  1417. nidus = a nest in which spiders or insects deposit their eggs
  1418. Niger = an African river
  1419. Niger River = an African river
  1420. Nile = the world's longest river (4150 miles); flows northward through eastern Africa into the Mediterranean
  1421. Nile River = the world's longest river (4150 miles); flows northward through eastern Africa into the Mediterranean
  1422. nimbus = a dark grey cloud bearing rain
  1423. nimbus cloud = a dark grey cloud bearing rain
  1424. Niobrara = a tributary of the Missouri River
  1425. Niobrara River = a tributary of the Missouri River
  1426. nodule = a small rounded lump of mineral substance
  1427. nonessential = anything that is not essential
  1428. Norma = a small constellation in the southern hemisphere near Lupus and Ara in the Milky Way
  1429. normal fault = an inclined fault in which the hanging wall appears to have slipped downward relative to the footwall
  1430. North America = a continent (the third largest) in the western hemisphere connected to South America by the Isthmus of Panama
  1431. North Atlantic = that part of the Atlantic Ocean to the north of the equator
  1432. North Channel = a strait between Northern Ireland and Scotland that connects the Atlantic Ocean and the Irish Sea
  1433. North Pacific = that part of the Pacific Ocean to the north of the equator
  1434. North Peak = 19,370 feet high
  1435. North Platte = a river that rises in northern Colorado and flows northward into Wyoming and then eastward and southeastward through Nebraska where it joins the South Platte to form the Platte River
  1436. North Platte River = a river that rises in northern Colorado and flows northward into Wyoming and then eastward and southeastward through Nebraska where it joins the South Platte to form the Platte River
  1437. North Sea = an arm of the North Atlantic between the British Isles and Scandinavia
  1438. North Star = the brightest star in Ursa Minor; at the end of the handle of the Little Dipper
  1439. Northern Cross = a cluster of 5 bright stars forming a cross in the constellation Cygnus
  1440. Norwegian Sea = the part of the Atlantic that lies off the Norwegian coast to the north of the North Sea
  1441. notch = the location in a range of mountains of a geological formation that is lower than the surrounding peaks
  1442. nova = a star that ejects some of its material in the form of a cloud and becomes more luminous in the process
  1443. nub = a small piece
  1444. nubbin = a small nub
  1445. nucleon = a constituent (proton or neutron) of an atomic nucleus
  1446. nucleus = the positively charged dense center of an atom / (astronomy) the center of the head of a comet
  1447. nugget = a solid lump of a precious metal (especially gold) as found in the earth
  1448. nullah = a ravine or gully in southern Asia
  1449. Nuptse = a mountain in the central Himalayas on the border of Tibet and Nepal
  1450. Ob = a major river of western Siberia
  1451. Ob River = a major river of western Siberia
  1452. obliterator = an eliminator that does away with all traces
  1453. ocean = a large body of water constituting a principal part of the hydrosphere
  1454. ocean bottom = the bottom of a sea or ocean
  1455. ocean floor = the bottom of a sea or ocean
  1456. oceanfront = land bordering an ocean
  1457. oceanic abyss = a long steep-sided depression in the ocean floor
  1458. Octans = the constellation that includes the southern celestial pole
  1459. Oder = a European river
  1460. Oder River = a European river
  1461. offing = the part of the sea that can be seen from the shore and is beyond the anchoring area
  1462. Ohio = a river that is formed in western Pennsylvania and flows westward to become a tributary of the Mississippi River
  1463. Ohio River = a river that is formed in western Pennsylvania and flows westward to become a tributary of the Mississippi River
  1464. oil-water interface = an interface forming the boundary between the non-miscible liquids oil and water
  1465. Ojos del Salado = a mountain in the Andes on the border between Argentina and Chile
  1466. Okeechobee = a lake in southeast Florida to the north of the Everglades
  1467. Okeechobee Waterway = a waterway used by small boats to travel between the Atlantic Ocean and the Gulf of Mexico through Lake Okeechobee and the Caloosahatchee Canal and the Caloosahatchee River
  1468. Okefenokee Swamp = a large swampy area of northeast Florida and southeast Georgia
  1469. Old Faithful = a geyser in Yellowstone National Park that erupts for about 4 minutes about every 65 minutes
  1470. Olduvai Gorge = a gorge in northeastern Tanzania where anthropologists have found some of the earliest human remains
  1471. Olimbos = a mountain peak in northeast Greece near the Aegean coast
  1472. Olympus = a mountain peak in northeast Greece near the Aegean coast
  1473. Omega Centauri = a global cluster in the constellation Centaurus
  1474. Onega = lake in northwestern Russia near the border with Finland
  1475. Ontario = the smallest of the Great Lakes
  1476. open chain = a chain of atoms in a molecule whose ends are not joined to form a ring
  1477. opening = an open or empty space in or between things
  1478. Ophiuchus = a large constellation in the equatorial region between Hercules and Scorpius
  1479. Orange = a river in South Africa that flows generally westward to the Atlantic Ocean
  1480. Orange River = a river in South Africa that flows generally westward to the Atlantic Ocean
  1481. ore bed = a stratum of ore
  1482. Orinoco = a South American river 1,500 miles long
  1483. Orinoco River = a South American river 1,500 miles long
  1484. Orion = a constellation on the equator to the east of Taurus
  1485. Osage = a river in Missouri that is a tributary of the Missouri River
  1486. Osage River = a river in Missouri that is a tributary of the Missouri River
  1487. Osaka Bay = a bay of the western Pacific in southern Honshu
  1488. Ottawa = a river in southeastern Canada that flows along the boundary between Quebec and Ontario to the Saint Lawrence River near Montreal
  1489. Ottawa river = a river in southeastern Canada that flows along the boundary between Quebec and Ontario to the Saint Lawrence River near Montreal
  1490. Ouachita = a river that rises in western Arkansas and flows southeast into eastern Louisiana to become a tributary of the Red River
  1491. Ouachita River = a river that rises in western Arkansas and flows southeast into eastern Louisiana to become a tributary of the Red River
  1492. Ouse = a river in northeastern England that flows generally southeastward to join the Trent River and form the Humber
  1493. Ouse River = a river in northeastern England that flows generally southeastward to join the Trent River and form the Humber
  1494. Outaouais = a river in southeastern Canada that flows along the boundary between Quebec and Ontario to the Saint Lawrence River near Montreal
  1495. outcrop = the part of a rock formation that appears above the surface of the surrounding land
  1496. outcropping = the part of a rock formation that appears above the surface of the surrounding land
  1497. outer planet = a major planet whose orbit is outside the asteroid belt
  1498. outflow = a natural flow of ground water
  1499. outpouring = a natural flow of ground water
  1500. outthrust = an outcropping of rock that extends outward
  1501. overburden = the surface soil that must be moved away to get at coal seams and mineral deposits
  1502. overthrust fault = a geological fault in which the upper side appears to have been pushed upward by compression
  1503. oxbow = a U-shaped curve in a stream / the land inside an oxbow bend in a river
  1504. oxbow lake = a crescent-shaped lake (often temporary) that is formed when a meander of a river is cut off from the main channel
  1505. Ozark Mountains = an area of low mountains in northwestern Arkansas and southeastern Missouri and northeastern Oklahoma
  1506. Ozark Plateau = an area of low mountains in northwestern Arkansas and southeastern Missouri and northeastern Oklahoma
  1507. Ozarks = an area of low mountains in northwestern Arkansas and southeastern Missouri and northeastern Oklahoma
  1508. ozone hole = an area of the ozone layer (near the poles) that is seasonally depleted of ozone
  1509. ozone layer = a layer in the stratosphere (at approximately 20 miles) that contains a concentration of ozone sufficient to block most ultraviolet radiation from the sun
  1510. ozonosphere = a layer in the stratosphere (at approximately 20 miles) that contains a concentration of ozone sufficient to block most ultraviolet radiation from the sun
  1511. Pacific = the largest ocean in the world
  1512. Pacific Coast = a coast of the Pacific Ocean
  1513. Pacific Ocean = the largest ocean in the world
  1514. pack ice = a large expanse of floating ice
  1515. Pallas = a large asteroid
  1516. pallasite = a meteorite composed principally of olivine and metallic iron
  1517. Palmer Peninsula = a large peninsula of Antarctica that extends some 1200 miles north toward South America
  1518. Pamir Mountains = a mountain range in central Asia that is centered in Tajikistan but extends into Kyrgyzstan and Afghanistan and Pakistan and western China
  1519. Pangaea = a hypothetical continent including all the landmass of the earth prior to the Triassic period when it split into Laurasia and Gondwanaland
  1520. Pangea = a hypothetical continent including all the landmass of the earth prior to the Triassic period when it split into Laurasia and Gondwanaland
  1521. Para = an estuary in northern Brazil into which the Tocantins River flows
  1522. Para River = an estuary in northern Brazil into which the Tocantins River flows
  1523. Parana = a South American river
  1524. Parana River = a South American river
  1525. paring = a thin fragment or slice (especially of wood) that has been shaved from something
  1526. Parnahiba = a river in northeastern Brazil that flows generally northward to the Atlantic Ocean
  1527. Parnaiba = a river in northeastern Brazil that flows generally northward to the Atlantic Ocean
  1528. Parnassus = a mountain in central Greece where (according to Greek mythology) the Muses lived
  1529. part = a portion of a natural object
  1530. particle = a body having finite mass and internal structure but negligible dimensions
  1531. Pas de Calais = the strait between the English Channel and the North Sea
  1532. pass = the location in a range of mountains of a geological formation that is lower than the surrounding peaks
  1533. path = a line or route along which something travels or moves
  1534. Paulo Afonso = a major waterfall in northeastern Brazil
  1535. Paulo Afonso Falls = a major waterfall in northeastern Brazil
  1536. Pavo = a small constellation near the South Pole between Tucana and Ara
  1537. Pearl River = a river in Mississippi that flows southward to the Gulf of Mexico / a river in southeast China that flows into the South China Sea
  1538. peat bog = wet spongy ground of decomposing vegetation; has poorer drainage than a swamp
  1539. pebble = a small smooth rounded rock
  1540. Pecos = a tributary of the Rio Grande that flows southeastward from New Mexico through western Texas
  1541. Pecos River = a tributary of the Rio Grande that flows southeastward from New Mexico through western Texas
  1542. Pee Dee = a river that flows through central North Carolina and northeastern South Carolina to the Atlantic Ocean
  1543. Pee Dee River = a river that flows through central North Carolina and northeastern South Carolina to the Atlantic Ocean
  1544. Pegasus = a constellation in the northern hemisphere near Andromeda and Pisces
  1545. peneplain = a more or less level land surface representing an advanced stage of erosion undisturbed by crustal movements
  1546. peneplane = a more or less level land surface representing an advanced stage of erosion undisturbed by crustal movements
  1547. peninsula = a large mass of land projecting into a body of water
  1548. Penobscot = a river in central Maine flowing into Penobscot Bay
  1549. Penobscot Bay = an inlet of the Atlantic in eastern Maine
  1550. Penobscot River = a river in central Maine flowing into Penobscot Bay
  1551. Perejil = a small uninhabited Mediterranean islet claimed by both Morocco and Spain
  1552. perforation = a hole made in something
  1553. permafrost = ground that is permanently frozen
  1554. Perseus = a conspicuous constellation in the northern hemisphere
  1555. Persian Gulf = a shallow arm of the Arabian Sea between Iran and the Arabian peninsula
  1556. petrifaction = a rock created by petrifaction
  1557. Phobos = the larger of the two satellites of Mars
  1558. Phoenix = a constellation in the southern hemisphere near Tucana and Sculptor
  1559. Phosphorus = a planet (usually Venus) seen just before sunrise in the eastern sky
  1560. photoelectron = an electron that is emitted from an atom or molecule by an incident photon
  1561. photon = a quantum of electromagnetic radiation
  1562. photosphere = the intensely luminous surface of a star
  1563. pi-meson = a meson involved in holding the nucleus together
  1564. Pictor = a constellation in the southern hemisphere near Dorado and Columba
  1565. piece = a portion of a natural object
  1566. piedmont = a gentle slope leading from the base of a mountain to a region of flat land
  1567. Piedmont glacier = a type of glaciation characteristic of Alaska
  1568. Piedmont type of glacier = a type of glaciation characteristic of Alaska
  1569. Pike's Peak = a mountain peak in the Rockies in central Colorado
  1570. Pillars of Hercules = the two promontories at the eastern end of the Strait of Gibraltar
  1571. pinetum = an area planted with pine trees or related conifers
  1572. Ping = a river in western Thailand
  1573. Ping River = a river in western Thailand
  1574. pion = a meson involved in holding the nucleus together
  1575. Pisces = a large faint zodiacal constellation
  1576. Pissis = a mountain in the Andes in Argentina
  1577. pit = a sizeable hole
  1578. placer = an alluvial deposit that contains particles of some valuable mineral
  1579. plage = the beach at a seaside resort
  1580. plain = extensive tract of level open land
  1581. planet = any of the nine large celestial bodies in the solar system that revolve around the sun and shine by reflected light; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto in order of their proximity to the sun
  1582. planetary nebula = a nebula that was once thought to be a star with its planets but is now thought to be a very hot star surrounded by an expanding envelope of ionized gases that emit a fluorescent glow because of intense radiation from the star
  1583. planetesimal = one of many small solid celestial bodies thought to have existed at an early stage in the development of the solar system
  1584. planetoid = any of numerous small celestial bodies that move around the sun
  1585. plasmid = a small cellular inclusion consisting of a ring of DNA that is not in a chromosome but is capable of autonomous replication
  1586. plasmid DNA = a small cellular inclusion consisting of a ring of DNA that is not in a chromosome but is capable of autonomous replication
  1587. Plata River = an estuary between Argentina and Uruguay
  1588. plate = a rigid layer of the Earth's crust that is believed to drift slowly
  1589. plateau = a relatively flat highland
  1590. Platte = a river in Nebraska that flows eastward to become a tributary of the Missouri River
  1591. Platte River = a river in Nebraska that flows eastward to become a tributary of the Missouri River
  1592. Plattensee = a large shallow lake in western Hungary
  1593. Pleiades = a star cluster in the constellation Taurus
  1594. Plough = a group of seven bright stars in the constellation Ursa Major
  1595. ploughland = arable land that is worked by plowing and sowing and raising crops
  1596. plowland = arable land that is worked by plowing and sowing and raising crops
  1597. Pluto = a large asteroid that was once thought to be the farthest known planet from the sun
  1598. Po = a European river
  1599. Po Hai = an inlet of the Yellow Sea, on the coast of Eastern China
  1600. Po River = a European river
  1601. Pobeda Peak = a mountain peak in the Tien Shan mountains in northern India
  1602. Pobedy Peak = a mountain peak in the Tien Shan mountains in northern India
  1603. point = a promontory extending out into a large body of water
  1604. polar glacier = a glacier near the Arctic or Antarctic poles
  1605. polar star = the brightest star in Ursa Minor; at the end of the handle of the Little Dipper
  1606. Polaris = the brightest star in Ursa Minor; at the end of the handle of the Little Dipper
  1607. polder = low-lying land that has been reclaimed and is protected by dikes
  1608. pole star = the brightest star in Ursa Minor; at the end of the handle of the Little Dipper
  1609. polestar = the brightest star in Ursa Minor; at the end of the handle of the Little Dipper
  1610. Pollux = the brightest star in Gemini
  1611. polynya = a stretch of open water surrounded by ice
  1612. pond = a small lake
  1613. pool = a small lake / a small body of standing water (rainwater) or other liquid
  1614. positive muon = the antiparticle of a muon
  1615. positron = an elementary particle with positive charge
  1616. pothole = a pit or hole produced by wear or weathering
  1617. Potomac = a river in the east central United States
  1618. Potomac River = a river in the east central United States
  1619. Poyang = a lake in central China that is connected to the Chang Jiang by a canal
  1620. precipice = a very steep cliff
  1621. primary = a celestial body (especially a star) relative to other objects in orbit around it
  1622. prion = an infectious protein particle similar to a virus but lacking nucleic acid
  1623. Procyon = the brightest star in Canis Minor
  1624. promontory = a natural elevation
  1625. protein molecule = any large molecule containing chains of amino acids linked by peptide bonds
  1626. proton = a stable particle with positive charge equal to the negative charge of an electron
  1627. Proxima = the nearest star to the sun
  1628. Proxima Centauri = the nearest star to the sun
  1629. Prudhoe Bay = a bay on the northern coast of Alaska where oil was discovered in 1968
  1630. pruning = something that has been pruned off of a plant
  1631. psi particle = a neutral meson with a large mass
  1632. ptyalith = calculus in a salivary gland
  1633. puddle = a small body of standing water (rainwater) or other liquid
  1634. Puget Sound = an inlet of the North Pacific in northwestern Washington State
  1635. pulp = any soft or soggy mass
  1636. pulsar = a degenerate neutron star; small and extremely dense
  1637. Puppis = a constellation in the southern hemisphere between Vela and Canis Major that shaped like the stern of a boat
  1638. Purus = a Brazilian river
  1639. Purus River = a Brazilian river
  1640. Pyrenees = a chain of mountains between France and Spain
  1641. Pyxis = a constellation in the southern hemisphere near Puppis and Antlia
  1642. quag = a soft wet area of low-lying land that sinks underfoot
  1643. quagmire = a soft wet area of low-lying land that sinks underfoot
  1644. Quaoar = a planetoid discovered in 2002
  1645. quark = hypothetical truly fundamental particle in mesons and baryons; there are supposed to be six flavors of quarks (and their antiquarks), which come in pairs
  1646. quasar = a starlike object that may send out radio waves and other forms of energy
  1647. quasi-stellar radio source = a starlike object that may send out radio waves and other forms of energy
  1648. Queen Charlotte Sound = an inlet of the Pacific Ocean off the coast of British Columbia
  1649. quickener = an agent that gives or restores life or vigor
  1650. quicksand = a pit filled with loose wet sand into which objects are sucked down
  1651. rabbit burrow = a hole in the ground as a nest made by wild rabbits
  1652. rabbit hole = a hole in the ground as a nest made by wild rabbits
  1653. rabbit warren = a series of connected underground tunnels occupied by rabbits
  1654. radiator = any object that radiates energy
  1655. radio source = an object that radiates radio waves
  1656. rain cloud = a dark grey cloud bearing rain
  1657. rainbow = an arc of colored light in the sky caused by refraction of the sun's rays by rain
  1658. Rainier = a mountain peak in central Washington; highest peak in the Cascade Range
  1659. raise = an upward slope or grade
  1660. Rakaposhi = a mountain peak in the Karakoram Range in northern Kashmir
  1661. range = a series of hills or mountains
  1662. range of mountains = a series of hills or mountains
  1663. rangeland = land suitable for grazing livestock
  1664. rapid = a part of a river where the current is very fast
  1665. Rappahannock = a river that flows across eastern Virginia into the Tidewater region
  1666. Rappahannock River = a river that flows across eastern Virginia into the Tidewater region
  1667. rathole = a hole (as in the wall of a building) made by rats
  1668. ravine = a deep narrow steep-sided valley
  1669. recess = an arm off of a larger body of water
  1670. Red = a tributary of the Mississippi River that flows eastward from Texas along the southern boundary of Oklahoma and through Louisiana
  1671. red dwarf = a small, old, relatively cool star
  1672. red dwarf star = a small, old, relatively cool star
  1673. red giant = a large, old, luminous star
  1674. red giant star = a large, old, luminous star
  1675. Red Planet = a small reddish planet that is the 4th from the sun and is periodically visible to the naked eye
  1676. Red River = a tributary of the Mississippi River that flows eastward from Texas along the southern boundary of Oklahoma and through Louisiana
  1677. Red Sea = a long arm of the Indian Ocean between northeast Africa and Arabia
  1678. reef = a submerged ridge of rock or coral near the surface of the water
  1679. Regulus = the brightest star in Leo
  1680. relaxer = any agent that produces relaxation
  1681. relict = geological feature that is a remnant of a pre-existing formation after other parts have disappeared
  1682. remains = a relic that has been excavated from the soil / any object that is left unused or still extant
  1683. renal calculus = a calculus formed in the kidney
  1684. rent = an opening made forcibly as by pulling apart
  1685. represser = an agent that represses
  1686. repressor = an agent that represses
  1687. Republican = a tributary of the Kansas River that flows from eastern Colorado eastward through Nebraska and Kansas
  1688. Republican River = a tributary of the Kansas River that flows from eastern Colorado eastward through Nebraska and Kansas
  1689. requirement = anything indispensable
  1690. requisite = anything indispensable
  1691. reservoir = anything (a person or animal or plant or substance) in which an infectious agent normally lives and multiplies
  1692. restriction fragment = the fragment of DNA that is produced by cleaving DNA with a restriction enzyme
  1693. retardant = any agent that retards or delays or hinders
  1694. retardation = any agent that retards or delays or hinders
  1695. retardent = any agent that retards or delays or hinders
  1696. Reticulum = a small constellation in the southern hemisphere near Dorado and Hydrus
  1697. reverse fault = a geological fault in which the upper side appears to have been pushed upward by compression
  1698. Rhein = a major European river carrying more traffic than any other river in the world
  1699. Rhine = a major European river carrying more traffic than any other river in the world
  1700. Rhine River = a major European river carrying more traffic than any other river in the world
  1701. Rhodope Mountains = a mountain range in the Balkan peninsula in southeastern Europe
  1702. Rhone = a major French river
  1703. Rhone River = a major French river
  1704. ribbon = any long object resembling a thin line
  1705. ridge = a long narrow natural elevation or striation / a long narrow range of hills / a long narrow natural elevation on the floor of the ocean
  1706. ridgeline = a long narrow range of hills
  1707. rift = a narrow fissure in rock / a gap between cloud masses
  1708. rift valley = a valley with steep sides
  1709. Rigel = the brightest star in Orion
  1710. Rigil = brightest star in Centaurus
  1711. Rigil Kent = brightest star in Centaurus
  1712. rill = a small channel (as one formed by soil erosion) / a small stream
  1713. ring = a chain of atoms in a molecule that forms a closed loop
  1714. Rio Bravo = a North American river; boundary between the United States and Mexico
  1715. Rio de la Plata = an estuary between Argentina and Uruguay
  1716. Rio Grande = a North American river; boundary between the United States and Mexico
  1717. rip = an opening made forcibly as by pulling apart
  1718. riparian forest = woodlands along the banks of stream or river
  1719. ripple mark = one of a series of small ridges produced in sand by water currents or by wind
  1720. rise = an upward slope or grade
  1721. river = a large natural stream of water
  1722. River Acheron = a river in Hades across which the souls of the dead were carried by Charon
  1723. River Adige = a river in northern Italy that flows southeast into the Adriatic Sea
  1724. River Aire = a river in northern England that flows southeast through West Yorkshire
  1725. River Arno = a river in central Italy rising in the Apennines and flowing through Florence and Pisa to the Ligurian Sea
  1726. River Avon = a river in central England that flows through Stratford-on-Avon and empties into the Severn / a river in southwestern England rising in Gloucestershire and flowing through Bristol to empty into the estuary of the Severn
  1727. river bottom = a channel occupied (or formerly occupied) by a river
  1728. river boulder = a boulder that has been carried by a river to a place remote from its place of origin
  1729. River Cam = a river in east central England that flows past Cambridge to join the Ouse River
  1730. River Cocytus = a river in Hades that was said to be a tributary of the Acheron
  1731. River Kasai = a river of southwestern Africa that rises in central Angola and flows east and then north (forming part of the border between Angola and Congo) and continuing northwest through Congo to empty into the Congo River on the border between Congo and Republic of the Congo
  1732. River Lethe = a river in Hades
  1733. River Severn = a river in England and Wales flowing into the Bristol Channel
  1734. River Styx = a river in Hades across which Charon carried dead souls
  1735. River Thames = the longest river in England
  1736. River Trent = a river in central England that flows generally northeastward to join with the Ouse River and form the Humber
  1737. River Tyne = a river in northern England that flows east to the North Sea
  1738. riverbank = the bank of a river
  1739. riverbed = a channel occupied (or formerly occupied) by a river
  1740. riverside = the bank of a river
  1741. rivulet = a small stream
  1742. rock = a lump or mass of hard consolidated mineral matter
  1743. rock outcrop = the part of a rock formation that appears above the surface of the surrounding land
  1744. Rockies = the chief mountain range of western North America; extends from British Columbia to northern New Mexico
  1745. Rocky Mountains = the chief mountain range of western North America; extends from British Columbia to northern New Mexico
  1746. roof = the inner top surface of a covered area or hollow space
  1747. Ross Sea = an arm of the southern Pacific Ocean in Antarctica
  1748. round = the course along which communications spread
  1749. row = a long continuous strip
  1750. Ruhr = a tributary of the Rhine
  1751. Ruhr River = a tributary of the Rhine
  1752. run = a small stream
  1753. runnel = a small stream
  1754. Rushmore = a mountain in the Black Hills of South Dakota
  1755. Russell's body = an inclusion body found in plasma cells in cases of cancer
  1756. Russian River = a river in northern California
  1757. Saale = a river that rises in central Germany and flows north to join the Elbe River
  1758. Saale River = a river that rises in central Germany and flows north to join the Elbe River
  1759. Sabine = a river in eastern Texas that flows south into the Gulf of Mexico
  1760. Sabine River = a river in eastern Texas that flows south into the Gulf of Mexico
  1761. Sacramento Mountains = mountain range in New Mexico to the east of the Rio Grande
  1762. Sacramento River = a river in northern California rising near Mount Shasta and flowing south to the San Francisco Bay
  1763. saddle = a pass or ridge that slopes gently between two peaks
  1764. saddleback = a pass or ridge that slopes gently between two peaks
  1765. Sagitta = a small constellation in the northern hemisphere between Cygnus and Aquila and crossed by the Milky Way
  1766. Sagittarius = a large zodiacal constellation in the southern hemisphere
  1767. Saint Francis = a tributary of the Mississippi River that rises in Missouri and flows southeastward through Arkansas
  1768. Saint Francis River = a tributary of the Mississippi River that rises in Missouri and flows southeastward through Arkansas
  1769. Saint John = a river that rises in Maine and flows northeastward through New Brunswick to empty into the Bay of Fundy
  1770. Saint John River = a river that rises in Maine and flows northeastward through New Brunswick to empty into the Bay of Fundy
  1771. Saint Johns = a river in northeastern Florida that flows northward to Jacksonville and then eastward to empty into the Atlantic Ocean
  1772. Saint Johns River = a river in northeastern Florida that flows northward to Jacksonville and then eastward to empty into the Atlantic Ocean
  1773. Saint Lawrence = a North American river
  1774. Saint Lawrence River = a North American river
  1775. Sajama = a mountain peak in the Andes in Bolivia
  1776. salivary calculus = a stone formed in the salivary gland
  1777. Salmon = a tributary of the Snake River in Idaho
  1778. Salmon River = a tributary of the Snake River in Idaho
  1779. salt flat = a flat expanse of salt left by the evaporation of a body of salt water
  1780. salt lick = a salt deposit that animals regularly lick
  1781. salt marsh = low-lying wet land that is frequently flooded with saltwater
  1782. salt plain = a flat expanse of salt left by the evaporation of a body of salt water
  1783. Salton Sea = a saltwater lake in southeastern California
  1784. saltpan = a shallow basin in a desert region
  1785. Samanala = a mountain peak in south central Sri Lanka
  1786. Sambre = a river in western Europe that rises in northern France and flows generally east into Belgium where it joins the Meuse at Namur
  1787. Sambre River = a river in western Europe that rises in northern France and flows generally east into Belgium where it joins the Meuse at Namur
  1788. sample = all or part of a natural object that is collected and preserved as an example of its class
  1789. San Andreas Fault = a major geological fault in California; runs from San Diego to San Francisco
  1790. San Diego Bay = a bay of the Pacific in southern California
  1791. San Fernando Valley = a fertile valley in southern California to the north of Los Angeles
  1792. San Francisco Bay = a bay of the Pacific in western California
  1793. San Joaquin River = a river in central California that rises in the Sierra Nevada and flows northwest to form a large delta with the Sacramento River
  1794. San Joaquin Valley = a vast valley in central California known for its rich farmland
  1795. San Juan Hill = a hill in eastern Cuba (near Santiago de Cuba) that was captured during the Spanish-American War
  1796. San Juan Mountains = a mountain range in southwestern Colorado that is part of the Rocky Mountains
  1797. sand bar = a bar of sand
  1798. sand dune = a ridge of sand created by the wind
  1799. sandbank = a submerged bank of sand near a shore or in a river
  1800. sandbar = a bar of sand
  1801. sandpit = a large pit in sandy ground from which sand is dug
  1802. sanitary landfill = a low area where waste is buried between layers of earth
  1803. Sao Francisco = a river in eastern Brazil flowing into the Atlantic Ocean
  1804. Saone = a river in eastern France
  1805. Saone River = a river in eastern France
  1806. Sargasso Sea = a vast area of the North Atlantic from the West Indies to the Azores that is dense with gulfweed
  1807. Saronic Gulf = a gulf of the Aegean on the southeastern coast of Greece
  1808. satellite = any celestial body orbiting around a planet or star
  1809. satisfier = any agent capable of producing satisfaction
  1810. Saturn = a giant planet that is surrounded by three planar concentric rings of ice particles
  1811. Savannah = a river in South Carolina that flows southeast to the Atlantic
  1812. Savannah River = a river in South Carolina that flows southeast to the Atlantic
  1813. sawpit = a pit over which lumber is positioned to be sawed by two men with a long two-handed saw
  1814. Sayan Mountains = a range of mountains in southern Siberia to the west of Lake Baikal
  1815. scablands = flat elevated land with poor soil and little vegetation that is scarred by dry channels of glacial origin
  1816. scale = a thin flake of dead epidermis shed from the surface of the skin
  1817. scarp = a long steep slope or cliff at the edge of a plateau or ridge
  1818. Scheldt = a river that rises in France and flows northeast across Belgium and empties into the North Sea
  1819. Scheldt River = a river that rises in France and flows northeast across Belgium and empties into the North Sea
  1820. Schwarzwald = a hilly forest region in southwestern Germany
  1821. scintilla = a sparkling glittering particle
  1822. scissure = a long narrow opening
  1823. Scorpio = a large zodiacal constellation between Libra and Sagittarius
  1824. Scorpius = a large zodiacal constellation between Libra and Sagittarius
  1825. scrap = a small fragment of something broken off from the whole
  1826. scraping = a fragment scraped off of something and collected
  1827. scree = a sloping mass of loose rocks at the base of a cliff
  1828. Sculptor = a faint constellation in the southern hemisphere near Phoenix and Cetus
  1829. scurf = a thin flake of dead epidermis shed from the surface of the skin / (botany) a covering that resembles scales or bran that covers some plant parts
  1830. sea = a division of an ocean or a large body of salt water partially enclosed by land
  1831. sea bottom = the bottom of a sea or ocean
  1832. sea floor = the bottom of a sea or ocean
  1833. Sea of Azof = a bay of the Black Sea between Russia and the Ukraine
  1834. Sea of Azoff = a bay of the Black Sea between Russia and the Ukraine
  1835. Sea of Azov = a bay of the Black Sea between Russia and the Ukraine
  1836. Sea of Cortes = a gulf to the west of the mainland of Mexico
  1837. Sea of Japan = an arm of the Pacific bordered by Japan, Korea, North Korea, and Russia
  1838. Sea of Marmara = an inland sea in northwestern Turkey
  1839. Sea of Marmora = an inland sea in northwestern Turkey
  1840. Sea of Okhotsk = an arm of the Pacific to the east of Asia
  1841. sea-coast = the shore of a sea or ocean
  1842. seabed = the bottom of a sea or ocean
  1843. seaboard = the shore of a sea or ocean regarded as a resort
  1844. seacoast = the shore of a sea or ocean
  1845. seamount = an underwater mountain rising above the ocean floor
  1846. seashore = the shore of a sea or ocean
  1847. seaside = the shore of a sea or ocean regarded as a resort
  1848. section = a very thin slice (of tissue or mineral or other substance) for examination under a microscope
  1849. sediment = matter that has been deposited by some natural process
  1850. Sedna = a planetoid of rock and ice about three-quarters the size of Pluto discovered in 2003
  1851. segment = one of the parts into which something naturally divides
  1852. seif dune = a long and tall sand dune with a sharp crest
  1853. Seine = a French river that flows through the heart of Paris and then northward into the English Channel
  1854. Seine River = a French river that flows through the heart of Paris and then northward into the English Channel
  1855. Selkirk Mountains = a range of the Rocky Mountains in southeastern British Columbia
  1856. Seneca Lake = a glacial lake in central New York
  1857. Serpens = a constellation in the equatorial region of the northern hemisphere near Ophiuchus and Corona Borealis
  1858. Sete Quedas = a great waterfall on the border between Brazil and Paraguay
  1859. settlings = sediment that has settled at the bottom of a liquid
  1860. seven seas = an informal expression for all of the oceans of the world
  1861. Severn = a river in England and Wales flowing into the Bristol Channel
  1862. Severn River = a river in England and Wales flowing into the Bristol Channel
  1863. Seyhan = a Turkish river flowing south southwest into the Mediterranean
  1864. Seyhan River = a Turkish river flowing south southwest into the Mediterranean
  1865. shag = a matted tangle of hair or fiber
  1866. shallow = a stretch of shallow water
  1867. Shari = an African river that flows northwest into Lake Chad
  1868. Shari River = an African river that flows northwest into Lake Chad
  1869. Shasta = a volcanic mountain peak in the Cascade Range in northern California
  1870. shaving = a thin fragment or slice (especially of wood) that has been shaved from something
  1871. sheet = any broad thin expanse or surface
  1872. shelf = a projecting ridge on a mountain or submerged under water
  1873. shelf ice = ice that is attached to land but projects out to sea
  1874. shell = a rigid covering that envelops an object / the exterior covering of a bird's egg
  1875. Shenandoah River = a river of northern Virginia that empties into the Potomac at Harpers Ferry
  1876. Shenandoah Valley = a large valley between the Allegheny Mountains and the Blue Ridge Mountains in northern Virginia
  1877. Sherman = a peak in the Rocky Mountains in central Colorado
  1878. Sherwood Forest = an ancient forest in central England; formerly a royal hunting ground
  1879. shift = a crack in the earth's crust resulting from the displacement of one side with respect to the other
  1880. shiner = something that shines
  1881. shoal = a stretch of shallow water / a sandbank in a stretch of water that is visible at low tide
  1882. shore = the land along the edge of a body of water
  1883. shore boulder = a boulder found on a shore remote from its place of origin
  1884. shoreline = a boundary line between land and water
  1885. shortener = any agent that shortens
  1886. sialolith = a stone formed in the salivary gland
  1887. side = an elevated geological formation
  1888. siderite = a meteorite consisting principally of nickel and iron
  1889. sierra = a range of mountains
  1890. Sierra Madre Occidental = a mountain range in northwestern Mexico that runs south from Arizona parallel to the Pacific coastline
  1891. Sierra Madre Oriental = a mountain range in northeastern Mexico the runs parallel to the coastline of the Gulf of Mexico
  1892. Sierra Nevada = a mountain range in eastern California
  1893. Sierra Nevada Mountains = a mountain range in eastern California
  1894. sill = a flat (usually horizontal) mass of igneous rock between two layers of older sedimentary rock
  1895. silva = the forest trees growing in a country or region
  1896. Sinai = a mountain peak in the southern Sinai Peninsula
  1897. sink = a depression in the ground communicating with a subterranean passage (especially in limestone) and formed by solution or by collapse of a cavern roof
  1898. sinkhole = a depression in the ground communicating with a subterranean passage (especially in limestone) and formed by solution or by collapse of a cavern roof
  1899. Sirius = the brightest star in the sky
  1900. Skagens Odde = a cape on the northernmost tip of Jutland between the Skagerrak and the Kattegatt
  1901. Skagerak = a broad strait of the North Sea between Jutland and Norway
  1902. Skagerrak = a broad strait of the North Sea between Jutland and Norway
  1903. Skaw = a cape on the northernmost tip of Jutland between the Skagerrak and the Kattegatt
  1904. ski slope = a snow-covered slope for skiing
  1905. skim = a thin layer covering the surface of a liquid
  1906. sky = the atmosphere and outer space as viewed from the earth
  1907. slack = a soft wet area of low-lying land that sinks underfoot / a stretch of water without current or movement
  1908. slack water = a stretch of water without current or movement
  1909. slash = an open tract of land in a forest that is strewn with debris from logging
  1910. slice = a thin flat piece cut off of some object
  1911. slit = a narrow fissure
  1912. sliver = a thin fragment or slice (especially of wood) that has been shaved from something / a small thin sharp bit or wood or glass or metal
  1913. slope = an elevated geological formation
  1914. slot = the trail of an animal
  1915. slough = any outer covering that can be shed or cast off (such as the cast-off skin of a snake) / a stagnant swamp (especially as part of a bayou) / a hollow filled with mud
  1916. Small Magellanic Cloud = the smaller of the two Magellanic Clouds visible from the southern hemisphere
  1917. snag = an opening made forcibly as by pulling apart
  1918. Snake = a long faint constellation in the southern hemisphere near the equator stretching between Virgo and Cancer / a tributary of the Columbia River that rises in Wyoming and flows westward
  1919. Snake River = a tributary of the Columbia River that rises in Wyoming and flows westward
  1920. snowcap = a covering of snow
  1921. snowdrift = a mass of snow heaped up by the wind
  1922. snowfield = a permanent wide expanse of snow
  1923. soap bubble = a bubble formed by a thin soap film
  1924. soapsuds = the froth produced by soaps or detergents
  1925. sod = surface layer of ground containing a mat of grass and grass roots
  1926. soil = material in the top layer of the surface of the earth in which plants can grow
  1927. solar system = the sun with the celestial bodies that revolve around it in its gravitational field
  1928. Solent = a strait of the English Channel between the coast of Hampshire and the Isle of Wight
  1929. solid ground = the solid part of the earth's surface
  1930. Solway Firth = a large firth on the west coast of Britain between England and Scotland
  1931. Sothis = the brightest star in the sky
  1932. sound = a large ocean inlet or deep bay / a narrow channel of the sea joining two larger bodies of water
  1933. source = anything (a person or animal or plant or substance) in which an infectious agent normally lives and multiplies
  1934. South America = a continent in the western hemisphere connected to North America by the Isthmus of Panama
  1935. South Atlantic = that part of the Atlantic Ocean to the south of the equator
  1936. South China Sea = a tropical arm of the Pacific Ocean near southeastern Asia subject to frequent typhoons
  1937. South Pacific = that part of the Pacific Ocean to the south of the equator
  1938. South Platte = a tributary of the Platte River
  1939. South Platte River = a tributary of the Platte River
  1940. South Sea = any sea to the south of the equator
  1941. South Sea Islands = any islands in the southern or southwestern of central parts of the Pacific Ocean
  1942. Southern Cross = a small conspicuous constellation in the southern hemisphere in the Milky Way near Centaurus
  1943. Southern Triangle = a small bright constellation in the polar region of the southern hemisphere near Circinus and Apus
  1944. spall = a fragment broken off from the edge or face of stone or ore and having at least one thin edge
  1945. spark = a small fragment of a burning substance thrown out by burning material or by friction
  1946. spawl = a fragment broken off from the edge or face of stone or ore and having at least one thin edge
  1947. Spica = the brightest star in Virgo
  1948. spit = a narrow strip of land that juts out into the sea
  1949. splint = a thin sliver of wood
  1950. splinter = a small thin sharp bit or wood or glass or metal
  1951. split = an opening made forcibly as by pulling apart / a lengthwise crack in wood
  1952. spoor = the trail left by a person or an animal
  1953. spring = a natural flow of ground water
  1954. spume = foam or froth on the sea
  1955. squark = a quark with an electric charge of -1/3 and a mass 988 times that of an electron and a strangeness of -1
  1956. St. Elias Mountains = a range of mountains between Alaska and the Yukon territory
  1957. St. Elias Range = a range of mountains between Alaska and the Yukon territory
  1958. St. Francis = a tributary of the Mississippi River that rises in Missouri and flows southeastward through Arkansas
  1959. St. Francis River = a tributary of the Mississippi River that rises in Missouri and flows southeastward through Arkansas
  1960. St. John = a river that rises in Maine and flows northeastward through New Brunswick to empty into the Bay of Fundy
  1961. St. John River = a river that rises in Maine and flows northeastward through New Brunswick to empty into the Bay of Fundy
  1962. St. Johns = a river in northeastern Florida that flows northward to Jacksonville and then eastward to empty into the Atlantic Ocean
  1963. St. Johns River = a river in northeastern Florida that flows northward to Jacksonville and then eastward to empty into the Atlantic Ocean
  1964. St. Lawrence = a North American river
  1965. St. Lawrence River = a North American river
  1966. stalactite = a cylinder of calcium carbonate hanging from the roof of a limestone cave
  1967. stalagmite = a cylinder of calcium carbonate projecting upward from the floor of a limestone cave
  1968. Stalin Peak = the highest mountain peak in the Pamir Mountains
  1969. star = a celestial body of hot gases that radiates energy derived from thermonuclear reactions in the interior / any celestial body visible (as a point of light) from the Earth at night
  1970. starlet = a small star
  1971. steep = a steep place
  1972. steppe = extensive plain without trees
  1973. stepping stone = a stone in a marsh or shallow water that can be stepped on in crossing
  1974. steps = the course along which a person has walked or is walking in
  1975. stercolith = a hard mass of fecal matter
  1976. Sterope = one of the stars in the star cluster Pleiades
  1977. stone = a lump or mass of hard consolidated mineral matter
  1978. Stony Tunguska = a river in Siberia that flows northwest to become a tributary of the Yenisei River
  1979. storm cloud = a heavy dark cloud presaging rain or a storm
  1980. straight chain = an open chain of atoms with no side chains
  1981. strait = a narrow channel of the sea joining two larger bodies of water
  1982. Strait of Calais = the strait between the English Channel and the North Sea
  1983. Strait of Dover = the strait between the English Channel and the North Sea
  1984. Strait of Georgia = the strait separating Vancouver Island from the Canadian mainland
  1985. Strait of Gibraltar = the strait between Spain and Africa
  1986. Strait of Hormuz = a strategically important strait linking the Persian Gulf and the Gulf of Oman
  1987. Strait of Magellan = the strait separating South America from Tierra del Fuego and other islands to the south of the continent; discovered by Ferdinand Magellan in 1520
  1988. Strait of Malacca = the strait between the Malay Peninsula and Sumatra
  1989. Strait of Messina = the strait separating Sicily from the tip of Italy
  1990. Strait of Ormuz = a strategically important strait linking the Persian Gulf and the Gulf of Oman
  1991. strand = a poetic term for a shore
  1992. strange particle = an elementary particle with non-zero strangeness
  1993. strange quark = a quark with an electric charge of -1/3 and a mass 988 times that of an electron and a strangeness of -1
  1994. stratosphere = the atmospheric layer between the troposphere and the mesosphere
  1995. stratus = a large dark low cloud
  1996. stratus cloud = a large dark low cloud
  1997. stream = a natural body of running water flowing on or under the earth
  1998. streambed = a channel occupied (or formerly occupied) by a stream
  1999. streamlet = a small stream
  2000. stressor = any agent that causes stress to an organism
  2001. stretch = a large and unbroken expanse or distance
  2002. strike-slip fault = a geological fault in which one of the adjacent surfaces appears to have moved horizontally
  2003. string = a hypothetical one-dimensional subatomic particle having a concentration of energy and the dynamic properties of a flexible loop
  2004. strip = a relatively long narrow piece of something
  2005. stub = a small piece / a short piece remaining on a trunk or stem where a branch is lost
  2006. Styx = a river in Hades across which Charon carried dead souls
  2007. subatomic particle = a body having finite mass and internal structure but negligible dimensions
  2008. subcontinent = a large and distinctive landmass (as India or Greenland) that is a distinct part of some continent
  2009. suds = the froth produced by soaps or detergents
  2010. Sun = the star that is the source of light and heat for the planets in the solar system / any star around which a planetary system revolves
  2011. Sun River = a river in western Montana that flows south and east to join the Missouri River
  2012. supergiant = an extremely bright star of very large diameter and low density
  2013. Superior = the largest freshwater lake in the world
  2014. superior planet = any of the planets whose orbit lies outside the earth's orbit
  2015. supernatant = the clear liquid that lies above a sediment or precipitate
  2016. supernova = a star that explodes and becomes extremely luminous in the process
  2017. superstring = a hypothetical particle that is the elementary particle in a theory of space-time
  2018. surface = the outermost level of the land or sea
  2019. Surinam River = a river in Suriname that flows northward to the Atlantic
  2020. Suriname River = a river in Suriname that flows northward to the Atlantic
  2021. Susquehanna = a river in the northeastern United States that rises in New York and flows southward through Pennsylvania and Maryland into Chesapeake Bay
  2022. Susquehanna River = a river in the northeastern United States that rises in New York and flows southward through Pennsylvania and Maryland into Chesapeake Bay
  2023. swale = a low area
  2024. swallow hole = a depression in the ground communicating with a subterranean passage (especially in limestone) and formed by solution or by collapse of a cavern roof
  2025. swamp = low land that is seasonally flooded
  2026. swampland = low land that is seasonally flooded
  2027. sward = surface layer of ground containing a mat of grass and grass roots
  2028. swath = a path or strip
  2029. swell = a rounded elevation
  2030. swimming hole = a small body of water (usually in a creek) that is deep enough to use for swimming
  2031. sylva = the forest trees growing in a country or region
  2032. table = flat tableland with steep edges
  2033. tableland = a relatively flat highland
  2034. Taconic Mountains = a range of the Appalachian Mountains along the eastern border of New York with Connecticut, Massachusetts, and Vermont
  2035. Tagus = a European river
  2036. Tagus River = a European river
  2037. Takakkaw = a waterfall in southeastern British Columbia
  2038. Tallapoosa = river that rises in northwestern Georgia and flows southwest through central Alabama to join the Coosa River near Montgomery and form the Alabama River
  2039. Tallapoosa River = river that rises in northwestern Georgia and flows southwest through central Alabama to join the Coosa River near Montgomery and form the Alabama River
  2040. talus = a sloping mass of loose rocks at the base of a cliff
  2041. Tampa Bay = an arm of the Gulf of Mexico in west central Florida
  2042. Tanganyika = the longest lake in the world in central Africa between Tanzania and Congo in the Great Rift Valley
  2043. tangle = a twisted and tangled mass that is highly interwoven
  2044. tar pit = a natural accumulation of bitumens at the surface of the earth
  2045. tarn = a mountain lake
  2046. tartar = an incrustation that forms on the teeth and gums
  2047. Tasman Sea = an arm of the southern Pacific Ocean between southeastern Australia and New Zealand
  2048. tau-minus particle = a lepton of very great mass
  2049. tau-plus particle = an antilepton of very great mass
  2050. tauon = a lepton of very great mass
  2051. Taurus = a zodiacal constellation in the northern hemisphere near Orion
  2052. tear = an opening made forcibly as by pulling apart
  2053. Telescopium = a small constellation in the southern hemisphere near Ara
  2054. Tennessee = a river formed by the confluence of two other rivers near Knoxville
  2055. Tennessee River = a river formed by the confluence of two other rivers near Knoxville
  2056. tent = a web that resembles a tent or carpet
  2057. teratogen = any agent that interferes with normal embryonic development: alcohol or thalidomide or X-rays or rubella are examples
  2058. terra firma = the solid part of the earth's surface
  2059. terrace = a level shelf of land interrupting a declivity
  2060. terrestrial planet = a planet having a compact rocky surface like the Earth's
  2061. territorial waters = the waters surrounding a nation and its territories over which that nation exercises sovereign jurisdiction
  2062. Teton Range = a mountain range in northwest Wyoming
  2063. Tevere = a river of central Italy
  2064. Thames = the longest river in England
  2065. Thames River = the longest river in England
  2066. the Alps = a large mountain system in south-central Europe
  2067. the Pamirs = a mountain range in central Asia that is centered in Tajikistan but extends into Kyrgyzstan and Afghanistan and Pakistan and western China
  2068. thermal spring = a natural spring of water at a temperature of 70 F or above
  2069. thermion = an electrically charged particle (electron or ion) emitted by a substance at a high temperature
  2070. thermosphere = the atmospheric layer between the mesosphere and the exosphere
  2071. thread = any long object resembling a thin line
  2072. thrust fault = a geological fault in which the upper side appears to have been pushed upward by compression
  2073. thundercloud = a dark cloud of great vertical extent charged with electricity
  2074. thunderhead = a rounded projecting mass of a cumulus cloud with shining edges
  2075. Tiber = a river of central Italy
  2076. tidal basin = a basin that is full of water at high tide
  2077. tidal river = a stream in which the effects of the tide extend far upstream
  2078. tidal stream = a stream in which the effects of the tide extend far upstream
  2079. tideland = land near the sea that is overflowed by the tide
  2080. tidewater = low-lying coastal land drained by tidal streams
  2081. tidewater river = a stream in which the effects of the tide extend far upstream
  2082. tidewater stream = a stream in which the effects of the tide extend far upstream
  2083. tideway = a channel in which a tidal current runs
  2084. Tien Shan = a major mountain range of central Asia
  2085. Tigris = an Asian river
  2086. Tigris River = an Asian river
  2087. tillage = arable land that is worked by plowing and sowing and raising crops
  2088. tilled land = arable land that is worked by plowing and sowing and raising crops
  2089. tilth = arable land that is worked by plowing and sowing and raising crops
  2090. timber = land that is covered with trees and shrubs
  2091. timberland = land that is covered with trees and shrubs
  2092. Timor Sea = an arm of the eastern Indian Ocean between Timor and northern Australia
  2093. Tirich Mir = a mountain in the Hindu Kush in Pakistan
  2094. Titan = the largest of the satellites of Saturn
  2095. Tocantins = a river in eastern Brazil that flows generally north to the Para River
  2096. Tocantins River = a river in eastern Brazil that flows generally north to the Para River
  2097. Tombigbee = a river that rises in northeastern Mississippi and flows southward through western Alabama to join the Alabama River and form the Mobile River
  2098. Tombigbee River = a river that rises in northeastern Mississippi and flows southward through western Alabama to join the Alabama River and form the Mobile River
  2099. tongue = a narrow strip of land that juts out into the sea
  2100. top quark = a hypothetical quark with a charge of +2/3 and a mass more than 100,000 times that of an electron
  2101. tophus = an incrustation that forms on the teeth and gums
  2102. tor = a high rocky hill / a prominent rock or pile of rocks on a hill
  2103. Torres Strait = a strait between northeastern Australia and southern New Guinea that connects the Coral Sea with the Arafura Sea
  2104. track = a line or route along which something travels or moves
  2105. trail = a track or mark left by something that has passed
  2106. transducing vector = a vector for delivering genes into cells
  2107. transmission mechanism = any mechanism whereby an infectious agent is spread from a reservoir to a human being
  2108. transmitter = any agent (person or animal or microorganism) that carries and transmits a disease
  2109. Transylvanian Alps = a range of the southern Carpathian Mountains extending across central Romania
  2110. Trapezium = a multiple star in the constellation of Orion
  2111. tree farm = a forest (or part of a forest) where trees are grown for commercial use
  2112. trench = a long steep-sided depression in the ocean floor
  2113. Trent = a river in central England that flows generally northeastward to join with the Ouse River and form the Humber
  2114. Trent River = a river in central England that flows generally northeastward to join with the Ouse River and form the Humber
  2115. Triangle = a small northern constellation near Perseus between Andromeda and Aries
  2116. Triangulum = a small northern constellation near Perseus between Andromeda and Aries
  2117. Triangulum Australe = a small bright constellation in the polar region of the southern hemisphere near Circinus and Apus
  2118. tributary = a branch that flows into the main stream
  2119. trichobezoar = a compact mass of hair that forms in the alimentary canal
  2120. Trinity River = a river in eastern Texas that is formed near Dallas and flows generally southeastward to Galveston Bay
  2121. Triton = the largest moon of Neptune
  2122. Trondheim Fiord = a long narrow inlet of the Norwegian Sea
  2123. Trondheim Fjord = a long narrow inlet of the Norwegian Sea
  2124. tropopause = the region of discontinuity between the troposphere and the stratosphere
  2125. troposphere = the lowest atmospheric layer
  2126. trough = a narrow depression
  2127. truth quark = a hypothetical quark with a charge of +2/3 and a mass more than 100,000 times that of an electron
  2128. Tucana = a large faint constellation in the southern hemisphere containing most of the Small Magellanic Cloud
  2129. Tugela = a major waterfall in southern Africa
  2130. Tugela Falls = a major waterfall in southern Africa
  2131. tundra = a vast treeless plain in the Arctic regions where the subsoil is permanently frozen
  2132. Tunguska = a river in southeastern Siberia that flows northwest from Lake Baikal to become a tributary of the Yenisei River / a river that arises to the north of Lake Baikal and flows north and west to the Yenisei River / a river in Siberia that flows northwest to become a tributary of the Yenisei River
  2133. tunnel = a hole made by an animal, usually for shelter
  2134. Tupungato = a mountain in the Andes on the border between Argentina and Chile
  2135. turf = surface layer of ground containing a mat of grass and grass roots
  2136. turning = a shaving created when something is produced by turning it on a lathe
  2137. twilight zone = the lowest level of the ocean to which light can reach
  2138. Twin = a waterfall in the Snake River in southern Idaho
  2139. Twin Falls = a waterfall in the Snake River in southern Idaho
  2140. twinkler = an object that emits or reflects light in an intermittent flickering manner
  2141. Tyan Shan = a major mountain range of central Asia
  2142. Tyne = a river in northern England that flows east to the North Sea
  2143. Tyne River = a river in northern England that flows east to the North Sea
  2144. Tyrolean Alps = a popular tourist area in the Tyrol
  2145. Tyrrhenian Sea = an arm of the Mediterranean between Italy and the islands of Corsica and Sardinia and Sicily
  2146. U.S. waters = territorial waters included within a distance of 12 nautical miles of the coasts of the United States and its territories
  2147. Ulugh Muz Tagh = a mountain in the Kunlun range in China
  2148. Ulugh Muztagh = a mountain in the Kunlun range in China
  2149. Uncompahgre Peak = the highest peak in the San Juan Mountains of southwestern Colorado
  2150. unit = a single undivided natural thing occurring in the composition of something else
  2151. unit cell = the smallest group of atoms or molecules whose repetition at regular intervals in three dimensions produces the lattices of a crystal
  2152. United States waters = territorial waters included within a distance of 12 nautical miles of the coasts of the United States and its territories
  2153. universe = everything that exists anywhere
  2154. up quark = a stable quark with an electric charge of +2/3 and a mass 607 times that of an electron
  2155. upgrade = an upward slope or grade
  2156. uphill = the upward slope of a hill
  2157. upland = elevated (e.g., mountainous) land
  2158. Upper Avon = a river in central England that flows through Stratford-on-Avon and empties into the Severn
  2159. Upper Avon River = a river in central England that flows through Stratford-on-Avon and empties into the Severn
  2160. upper mantle = the upper part of the mantle
  2161. Upper Peninsula = the peninsula between Lake Superior and Lake Michigan that forms the northwestern part of Michigan
  2162. Upper Tunguska = a river in southeastern Siberia that flows northwest from Lake Baikal to become a tributary of the Yenisei River
  2163. Ural Mountains = a mountain range in western Russia extending from the Arctic to the Caspian Sea
  2164. Urals = a mountain range in western Russia extending from the Arctic to the Caspian Sea
  2165. Uranus = a giant planet with a ring of ice particles
  2166. urinary calculus = a calculus formed in the kidney
  2167. Urmia = a shallow saline lake in northwestern Iran between Tabriz and the western border of Turkey
  2168. urolith = a urinary stone
  2169. Ursa Major = a constellation outside the zodiac that rotates around the North Star
  2170. Ursa Minor = a constellation outside the zodiac that rotates around the North Star
  2171. Urubupunga = a waterfall in the Parana river in Brazil
  2172. Urubupunga Falls = a waterfall in the Parana river in Brazil
  2173. Uruguay River = a South American river that arises in southern Brazil and flows south to the Rio de la Plata
  2174. vagabond = anything that resembles a vagabond in having no fixed place
  2175. vale = a long depression in the surface of the land that usually contains a river
  2176. valence electron = an electron in the outer shell of an atom which can combine with other atoms to form molecules
  2177. valley = a long depression in the surface of the land that usually contains a river
  2178. Vanern = a lake in southwestern Sweden
  2179. variable = something that is likely to vary
  2180. variable star = a star that varies noticeably in brightness
  2181. vector = any agent (person or animal or microorganism) that carries and transmits a disease
  2182. vector-borne transmission = indirect transmission of an infectious agent that occurs when a vector bites or touches a person
  2183. Vega = the brightest star in the constellation Lyra
  2184. vehicle = any inanimate object (as a towel or money or clothing or dishes or books or toys etc.) that can transmit infectious agents from one person to another
  2185. vehicle-borne transmission = indirect transmission of an infectious agent that occurs when a vehicle (or fomite) touches a person's body or is ingested
  2186. vein = a layer of ore between layers of rock
  2187. Vela = a constellation in the southern hemisphere between Carina and Pyxis
  2188. vent = a fissure in the earth's crust (or in the surface of some other planet) through which molten lava and gases erupt
  2189. Venus = the second nearest planet to the sun; it is peculiar in that its rotation is slow and retrograde
  2190. versant = the side or slope of a mountain
  2191. Vesper = a planet (usually Venus) seen at sunset in the western sky
  2192. Vesta = the brightest asteroid but the fourth to be discovered
  2193. vesture = something that covers or cloaks like a garment
  2194. Vetluga = a river in central Russia
  2195. Vetluga River = a river in central Russia
  2196. Victoria = a waterfall in the Zambezi River on the border between Zimbabwe and Zambia
  2197. Victoria Falls = a large waterfall on the border between Argentina and Brazil / a waterfall in the Zambezi River on the border between Zimbabwe and Zambia
  2198. Victoria Nyanza = the largest lake in Africa and the 2nd largest fresh water lake in the world
  2199. viral delivery vector = a transducing vector that uses a retrovirus
  2200. Virgo = a large zodiacal constellation on the equator
  2201. virino = a hypothetical infectious particle thought to be the cause of scrapie and other degenerative diseases of the central nervous system
  2202. Vistula = a European river
  2203. Vistula River = a European river
  2204. Volans = a small constellation in the polar region of the southern hemisphere near Dorado and Carina
  2205. volcanic crater = a bowl-shaped geological formation at the top of a volcano
  2206. volcano = a fissure in the earth's crust (or in the surface of some other planet) through which molten lava and gases erupt / a mountain formed by volcanic material
  2207. Volga = a Russian river; the longest river in Europe
  2208. Volga River = a Russian river; the longest river in Europe
  2209. Volkhov = a river in northwestern Russia flowing generally north into Lake Ladoga
  2210. Volkhov River = a river in northwestern Russia flowing generally north into Lake Ladoga
  2211. Volta = a river in Ghana that flows south to the Bight of Benin
  2212. Vulpecula = a constellation in the northern hemisphere near Cygnus and Sagitta
  2213. Wabash = a tributary of the Ohio River that rises in western Ohio and flows southwestward across Indiana
  2214. Wabash River = a tributary of the Ohio River that rises in western Ohio and flows southwestward across Indiana
  2215. wadi = gully or streambed in northern Africa and the Middle East that remains dry except during rainy season
  2216. Wagon = a group of seven bright stars in the constellation Ursa Major
  2217. Wain = a group of seven bright stars in the constellation Ursa Major
  2218. wall = anything that suggests a wall in structure or function or effect / a vertical (or almost vertical) smooth rock face
  2219. wall rock = a rock immediately adjacent to a vein or fault
  2220. wallow = a puddle where animals go to wallow
  2221. want = anything that is necessary but lacking
  2222. warren = a series of connected underground tunnels occupied by rabbits
  2223. wash = the dry bed of an intermittent stream
  2224. wasp's nest = habitation for wasps or hornets
  2225. wasps' nest = habitation for wasps or hornets
  2226. water = the part of the earth's surface covered with water
  2227. water gap = a pass in a mountain ridge through which a stream flows
  2228. water hole = a natural hole or hollow containing water
  2229. water level = underground surface below which the ground is wholly saturated with water
  2230. water system = a river and all of its tributaries
  2231. water table = underground surface below which the ground is wholly saturated with water
  2232. watercourse = a natural body of running water flowing on or under the earth / natural or artificial channel through which water flows
  2233. waterfall = a steep descent of the water of a river
  2234. waterside = land bordering a body of water
  2235. waterway = a navigable body of water
  2236. weakener = that which weakens or causes a loss of strength
  2237. weakly interacting massive particle = a hypothetical subatomic particle of large mass that interacts weakly with ordinary matter through gravitation
  2238. web = an intricate network suggesting something that was formed by weaving or interweaving
  2239. webbing = something forming a web
  2240. Weddell Sea = an arm of the south Atlantic in Antarctica to the east of the Antarctic Peninsula
  2241. Weisshorn = a mountain in the Alps in Switzerland
  2242. Weser = a river in northwestern Germany that flows northward to the North Sea near Bremerhaven
  2243. Weser River = a river in northwestern Germany that flows northward to the North Sea near Bremerhaven
  2244. wetland = a low area where the land is saturated with water
  2245. Wheeler Peak = a mountain peak in northeastern New Mexico in the Rocky Mountains
  2246. whin = any of various hard colored rocks
  2247. whinstone = any of various hard colored rocks
  2248. White = a tributary of the Mississippi River that flows southeastward through northern Arkansas and southern Missouri
  2249. white dwarf = a faint star of enormous density
  2250. white dwarf star = a faint star of enormous density
  2251. White Nile = a headstream of the Nile
  2252. White River = a tributary of the Mississippi River that flows southeastward through northern Arkansas and southern Missouri
  2253. White Sea = a large inlet of the Barents Sea in the northwestern part of European Russia
  2254. white water = frothy water as in rapids or waterfalls
  2255. whitewater = frothy water as in rapids or waterfalls
  2256. Whitney = the highest peak in the Sierra Nevada range in California
  2257. Wight = an isle and county of southern England in the English Channel
  2258. wild blue yonder = the sky as viewed during daylight
  2259. Wilderness = a wooded region in northeastern Virginia near Spotsylvania where bloody but inconclusive battles were fought in the American Civil War
  2260. Willamette = a river in western Oregon that flows north into the Columbia River near Portland
  2261. Willamette River = a river in western Oregon that flows north into the Columbia River near Portland
  2262. Wilson = a peak in the San Juan mountains of Colorado
  2263. WIMP = a hypothetical subatomic particle of large mass that interacts weakly with ordinary matter through gravitation
  2264. wind gap = a pass in a mountain ridge with no stream flowing through it
  2265. window = an opening that resembles a window in appearance or function
  2266. Windward Passage = a channel between eastern Cuba and western Haiti that connects the Atlantic Ocean with the Caribbean Sea
  2267. Winnipeg = a lake in southern Canada in Manitoba
  2268. Wisconsin = a tributary of the Mississippi River in Wisconsin
  2269. Wisconsin River = a tributary of the Mississippi River in Wisconsin
  2270. wonderland = a place or scene of great or strange beauty or wonder
  2271. woodland = land that is covered with trees and shrubs
  2272. world = the 3rd planet from the sun
  2273. wormcast = fossil trail of a worm
  2274. wormhole = hole made by a burrowing worm
  2275. xenolith = a piece of rock of different origin from the igneous rock in which it is embedded
  2276. Yalu = river in eastern Asia
  2277. Yalu River = river in eastern Asia
  2278. Yangtze = the longest river of Asia
  2279. Yangtze Kiang = the longest river of Asia
  2280. Yangtze River = the longest river of Asia
  2281. Yazoo = a river that rises in west central Mississippi and flows southwest to empty into the Mississippi River above Vicksburg
  2282. Yazoo River = a river that rises in west central Mississippi and flows southwest to empty into the Mississippi River above Vicksburg
  2283. Yellow River = a major river of Asia in northern China; flows generally eastward into the Yellow Sea
  2284. Yellow Sea = part of the Pacific off the east coast of Asia
  2285. Yellowstone = a tributary of the Missouri River that flows through the Yellowstone National Park
  2286. Yellowstone River = a tributary of the Missouri River that flows through the Yellowstone National Park
  2287. Yenisei = a Russian river in Siberia
  2288. Yenisei River = a Russian river in Siberia
  2289. Yenisey = a Russian river in Siberia
  2290. Yenisey River = a Russian river in Siberia
  2291. Yerupaja = a mountain peak in the Andes in Peru
  2292. Yosemite = a series of waterfalls in Yosemite National Park in California
  2293. Yosemite Falls = a series of waterfalls in Yosemite National Park in California
  2294. Yukon = a North American river that flows westward from the Yukon Territory through central Alaska to the Bering Sea
  2295. Yukon River = a North American river that flows westward from the Yukon Territory through central Alaska to the Bering Sea
  2296. Zaire River = a major African river
  2297. Zambezi = an African river
  2298. Zambezi River = an African river
  2299. Zhu Jiang = a river in southeast China that flows into the South China Sea
  2300. Zuider Zee = a former inlet of the North Sea in the northern coast of the Netherlands

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