Noun

(en noun)

The action of the verb warn; an instance of warning someone.

* , chapter=7

, title= The Mirror and the Lamp , passage=“[…] Churchill, my dear fellow, we have such greedy sharks, and wolves in lamb's clothing. Oh, dear, there's so much to tell you, so many warnings to give you, but all that must be postponed for the moment.”}}

Something spoken or written that is intended to warn.

* {{quote-magazine, date=2013-06-22, volume=407, issue=8841, page=76, magazine=(The Economist)

, title= Snakes and ladders , passage=Risk is everywhere. From tabloid headlines insisting that coffee causes cancer (yesterday, of course, it cured it) to stern government warnings about alcohol and driving, the world is teeming with goblins.}}

Noun

(en noun)

A sign made to give notice of some occurrence, command, or danger, or to indicate the start of a concerted action.

* Milton

All obeyed / The wonted signal and superior voice / Of this great potentate.

An on-off light, semaphore, or other device used to give an indication to another person.

(of a radio, TV, telephone, internet, etc) An electrical or electromagnetic action, normally a voltage that is a function of time that conveys the information of the radio or TV program or of communication with another party.

My mobile phone can't get a signal in the railway station.

A token; an indication; a foreshadowing; a sign.

* Shakespeare

The weary sun / Gives signal of a goodly day to-morrow.

* De Foe

There was not the least signal of the calamity to be seen.

Useful information, as opposed to noise.

(computing, Unix) A simple interprocess communication used to notify a process or thread of an occurrence.