Channel

In general, channel refers to the path between two endpoints. It can be used to mean specific types of channels, including:

In communications, a channel is the route which a message follows, as it is transmitted between a communication source and a receiver. See channel (communications).

In geography and nautical/shipping contexts, channel means the course traveled by a body of water or the passage of a ship between land masses. See channel (geography).

In digital imaging, a channel is the black and white representation of a specific color; by extension, the representation of a mask. See channel (digital image)