For the geographical meanings of this word, see channel (geography).

In communications, a "channel" is the "path" or "route" which a message follows, as it is transmitted between a communication source and a receiver. More specifically, in telecommunications, the term has the following definitions:

1. A connection between initiating and terminating nodes of a circuit.
2. A single path provided by a transmission medium via either
   1. physical separation, such as by multipair cable or
   2. electrical separation, such as by frequency- or time-division multiplexing.
3. A path for conveying electrical or electromagnetic signals, usually distinguished from other parallel paths.
4. The portion of a storage medium, such as a track or a band, that is accessible to a given reading or writing station or head.
5. In a communications system, the part that connects a data source to a data sink.
6. A specific radio frequency or band of frequencies, usually in conjunction with a predetermined letter, number, or codeword, and allocated by international agreement. For example 802.11b consists of unlicensed channels 1-13 from 2412MHz to 2484MHz in 5MHz steps.
7. In particular, a television channel. Examples include North American TV Channel 2 = 55.25MHz, Channel 13 = 211.25MHz
8. "channels" in Internet Relay Chat (IRC) which are named and based upon digital distinction as opposed to analog distinction.
9. An ion channel is a gate in a membrane that allows the passage of certain types of molecules.

See also: interference, baseband