(1) A transmission path .
(2) A set of properties that distinguishes one channel from another. For example, TV channels refer to particular frequencies at which radio waves are transmitted. IRC channels refer to specific discussions.
(3) In sales and marketing, the way in which a vendor communicates with and sells products to consumers.
(6) In audio and sound terms channel refers to an individual discrete audio track. When referring to more than two channels it is called multichannel.