is a specific kind of: communication.

is a broader term that covers: recording | number, phone number, telephone number | start, starting signal | storm signal | beam, radio beam | ticktack | time signal | dog-ear | animal communication | alarm, alarum, alert, warning signal | distress call, distress signal | all clear | bugle call | curfew | retreat | drumbeat | radiotelegraphic signal, telegraphic signal | whistle, whistling | high sign | symbol | visual signal | indicator | electronic signal | radio beacon | input, input signal | output, output signal ... show more.

derivation: bless, sign | bespeak, betoken, indicate, point, signal | distinguish, signalise, signalize | call attention, point out, signalise, signalize | signify | sign, signal, signalise, signalize | signalise, signalize.