'Signal' is Latin for 'a mark sent deliberately' — a sign with communicative intent.
A gesture, action, or sound used to convey information or instructions; to transmit information by means of a gesture, action, or sound; notably good or bad; outstanding.
From Latin 'signālis' (used as a sign), from 'signum' (a mark, sign, standard, military ensign, seal), from PIE *sekʷ- (to follow, to point out) or possibly *seg- (to hold), both debated. Latin 'signum' was a military standard — the emblem troops followed — which gave the word its dual character: a sign both marks and commands action. 'Signum' generates 'sign,' 'signal,' 'signify,' 'signature,' 'design' (to mark out), 'assign' (to mark to someone), 'resign' (to unsign, to give
In information theory, the 'signal-to-noise ratio' measures how much of a transmitted message is genuine information (signal) versus random interference (noise). Claude Shannon's 1948 paper on information theory formalized this concept, and the phrase has become a general metaphor: 'What's the signal-to-noise ratio of this meeting?' means 'How much useful content versus