mouth_of_the_watercourse distributary
A river is a natural flowing watercourse , usually freshwater , flowing towards an ocean , ___MASK77___ , lake or another river . In some cases a river flows into the ground and becomes dry at the end of its course without reaching another body of water . Small rivers can be referred to using names such as stream , creek , brook , rivulet , and rill . There are no official definitions for the generic term river as applied to geographic features , although in some countries or communities a stream is defined by its size . Many names for small rivers are specific to geographic location ; examples are " run " in some parts of the United States , " burn " in Scotland and northeast England , and " beck " in northern England . Sometimes a river is defined as being larger than a creek , but not always : the language is vague . Classical antiquity ( also the classical era , classical period or classical age ) is a term for a long period of cultural history centered on the Mediterranean ___MASK77___ , comprising the interlocking civilizations of ancient Greece and ancient Rome , collectively known as the Greco - Roman world . It is the period in which Greek and Roman society flourished and wielded great influence throughout Europe , North Africa and Southwestern Asia . A tributary or affluent is a stream or river that flows into a larger stream or ___MASK93___ stem ( or parent ) river or a lake . A tributary does not flow directly into a ___MASK77___ or ocean . Tributaries and the ___MASK93___ stem river drain the surrounding drainage basin of its surface water and groundwater , leading the water out into an ocean . A stream is a body of water with a current , confined within a bed and banks . Depending on its location or certain characteristics , a stream may be referred to as a " bayou ", " beck ", " branch ", " brook ", " burn ", " creek ", " crick ", " ghyll ", " gill ", " kill ", " lick ", " mill race ", " race ", " rill ", " river ", " rivulet ", " run ", " runnel ", " streamage ", " syke ", or " wash ". An alluvial fan is a fan - or cone - shaped deposit of sediment crossed and built up by streams . If a fan is built up by debris flows it is properly called a debris cone or colluvial fan . These flows come from a single point source at the apex of the fan , and over time move to occupy many positions on the fan surface . Fans are typically found where a canyon draining from mountainous terrain emerges out onto a flatter plain , and especially along fault - bounded mountain fronts . A distributary , or a distributary channel , is a stream that branches off and flows away from a ___MASK93___ stream channel . They are a common feature of river deltas . The phenomenon is known as river bifurcation . The opposite of a distributary is a tributary . Distributaries usually occur as a stream nears a lake or the ocean , but they can occur inland as well , such as on alluvial fans or when a tributary stream bifurcates as it nears its confluence with a larger stream . In some cases , a minor distributary can divert so much water from the ___MASK93___ channel that it can become the ___MASK93___ route . Sediment is a naturally occurring material that is broken down by processes of weathering and erosion , and is subsequently transported by the action of wind , water , or ice , and / or by the force of gravity acting on the particles . For example , sand and silt can be carried in suspension in river water and on reaching the ___MASK77___ be deposited by sedimentation and if buried this may eventually become sandstone and siltstone , ( sedimentary rocks ). The World Ocean or global ocean ( colloquially the ___MASK77___ or the ocean ) is the interconnected system of Earth ' s oceanic waters , and comprises the bulk of the hydrosphere , covering almost 71 % of Earth ' s surface , with a total volume of 1 . 332 billion cubic kilometers ( 351 quintillion US gallons ). A ___MASK77___ is a large body of salt water that is surrounded in whole or in part by land . More broadly , " the ___MASK77___ " is the interconnected system of Earth ' s salty , oceanic waters  considered as one global ocean or as several principal oceanic divisions . The ___MASK77___ moderates Earth ' s climate and has important roles in the water cycle , carbon cycle , and nitrogen cycle . Although the ___MASK77___ has been traveled and explored since prehistory , the modern scientific study of the ___MASK77___  oceanography  dates broadly to the British " Challenger " expedition of the 1870s . The ___MASK77___ is conventionally divided into up to five large oceanic sections  including the International Hydrographic Organization ' s four named oceans ( the Atlantic , Pacific , Indian , and Arctic ) and the Southern Ocean ; smaller , second - order sections , such as the Mediterranean , are known as " seas ". An ocean ( the ___MASK77___ of classical antiquity ) is a body of saline water that composes much of a planet ' s hydrosphere . On Earth , an ocean is one of the major conventional divisions of the World Ocean , which covers almost 71 % of its surface . These are , in descending order by area , the Pacific , Atlantic , Indian , Southern ( Antarctic ), and Arctic Oceans . The word " ___MASK77___ " is often used interchangeably with " ocean " in American English but , strictly speaking , a ___MASK77___ is a body of saline water ( generally a division of the world ocean ) partly or fully enclosed by land . In usage in the United States , a bayou ( or , from Cajun French ) is a body of water typically found in a flat , low - lying area , and can be either an extremely slow - moving stream or river ( often with a poorly defined shoreline ), or a marshy lake or wetland . The name " bayou " can also refer to a creek whose current reverses daily due to tides and which contains brackish water highly conducive to fish life and plankton . Bayous are commonly found in the Gulf Coast region of the southern United States , notably the ___MASK83___ Delta , with the states of Louisiana and Texas being famous for them . A bayou is frequently an anabranch or minor braid of a braided channel that is moving much more slowly than the mainstem , often becoming boggy and stagnant . Though fauna varies by region , many bayous are home to crawfish , certain species of shrimp , other shellfish , catfish , frogs , toads , American alligators , American crocodiles , herons , turtles , spoonbills , snakes , leeches , and a myriad of other species . Etymology . The word was first used by the English in Louisiana and is thought to originate from the Choctaw word " bayuk ", which means " small stream ". The first settlements of Bayou Teche , and other bayous , were by the Creoles , and that is why bayous are associated with Creole culture . " ___MASK93___ Stem " is 1942 instrumental by Duke Ellington and His Famous Orchestra . Although recorded in 1942 , the single would not be released until 1944 where it was Duke Ellington ' s last of four number one ' s on the Harlem Hit Parade . " ___MASK93___ Stem " also peaked at number twenty on the pop chart . A drainage basin or catchment basin is an extent or an area of land where all surface water from rain , melting snow , or ice converges to a single point at a lower elevation , usually the exit of the basin , where the waters join another body of water , such as a river , lake , reservoir , estuary , wetland , ___MASK77___ , or ocean . Thus if a tributary stream joins a brook that in turn joins a small river which is a tributary of a larger river , there is a series of successively larger ( and lower elevation ) drainage basins . For instance , the Missouri and Ohio rivers are within their own drainage basins and also within the drainage basin of the Mississippi River . Water is a transparent and nearly colorless chemical substance that is the ___MASK93___ constituent of Earth ' s streams , lakes , and oceans , and the fluids of most living organisms . Its chemical formula is HO , meaning that its molecule contains one oxygen and two hydrogen atoms , that are connected by covalent bonds . Water strictly refers to the liquid state of that substance , that prevails at standard ambient temperature and pressure ; but it often refers also to its solid state ( ice ) or its gaseous state ( steam or water vapor ). It also occurs in nature as snow , glaciers , ice packs and icebergs , clouds , fog , dew , aquifers , and atmospheric humidity .