Signal

A signal may be:

• An abstract element of information, or more exactly usually a flow of information (in either one or several dimensions). See Signal (information theory)

• In computing, an asynchronous event transmitted between one process and another (in Linux, UNIX and other POSIX-compliant operating systems, and also in several real-time operating system).

• A means of controlling road vehicles, pedestrians or trains. See Traffic signal, Pedestrian crossing or Railway signal.

• In a partnership card game, a player's choice of card to play at a particular time, which gives information to her partner. See Signal (contract bridge).

• Signal processing, noise (physics).