Middle English, from Old English, Anglo-French, & Latin; Old English lacu stream, pool, from Latin lacus lake, pool, pit & Anglo-French lac pit, from Latin lacus; akin to Old English lagu sea, Greek lakkos pond
- Date: 12th century
- a considerable inland body of standing water; also : a pool of other liquid (as lava, oil, or pitch)
A lake (from Latin lacus) is a terrain feature (or physical feature), a body of liquid on the surface of a world that is localized to the bottom of basin (another type of landform or terrain feature; that is, it is not global). Another definition is a body of fresh or salt water of considerable size that is surrounded by land. On Earth a body of water is considered a lake when it is inland, not part of the ocean, is larger and deeper than a pond. The only world other than Earth known to harbor lakes is Titan, Saturn's largest moon, which has lakes of ethane, most likely mixed with methane. It is not known if Titan's lakes are fed by rivers; Titan's surface is carved by numerous river beds. There is evidence that Mars once held lakes of water.
Natural lakes on Earth are generally found in mountainous areas, rift zones, and areas with ongoing or recent glaciation. Other lakes are found in endorheic basins or along the courses of mature rivers. In some parts of the world there are many lakes because of chaotic drainage patterns left over from the last Ice Age. All lakes are temporary over geologic time scales, as they will slowly fill in with sediments or spill out of the basin containing them.