A river is a stream of water, one that flows continuously. A lake is a closed depression in the earth’s crust, filled with water.
A river has parts – an estuary (the end of a river where it flows into another body of water – a lake, river, sea, or reservoir), rapids (a rocky area where water flows more rapidly), waterfalls, and ripples (shallow areas). Lakes have no such parts.
Rivers are invariably freshwater. Lakes can be either freshwater or saltwater. For example, in the southern desert plain of Bolivia there is Lake Uyuni, the saltiest lake in the world.
The nourishment of rivers and lakes also differs. Lakes can be fed from groundwater, surface water and from rivers flowing into them. A river, on the other hand, uses only the first two methods.