In physical geography, a channel is the physical confine of a river or slough, consisting of a bed and banks. See Stream bed.

A channel is also the natural or man-made deeper course through a reef, bar, bay, or any shallow body of water; also the navigable part of a river. See also: Ship canal.

The term channel is another word for strait, which is a relatively narrow body of water that connects two larger bodies of water. In this nautical context, the terms strait, channel, sound, and passage are synonymous and usually interchangeable. For example, in an archipelago, the water between islands is typically called a channel or passage. The English Channel is the strait between England and France.