# signal

Pronunciation: say "SIG-nuhl" /ˈsɪɡnəl/

## Noun

1. A sign made to give notice of an event, command, or danger, or to mark the start of a coordinated action.
   - Simple: A sign or movement that warns people, gives an order, or tells them to begin doing something together.
   - _The general waited for the signal before ordering his troops forward._
   - _Two short horn blasts served as the signal for all crews to abandon ship._
2. An electromagnetic action, usually a time-varying voltage, that carries the information of a radio or TV program or a communication with another party.
   - Simple: An electrical wave that carries radio, TV, or phone information through the air or along a wire.
   - _The antenna picked up a faint signal from the distant station._
   - _Engineers boosted the signal so the broadcast reached rural homes._
4. A device such as an on-off light or semaphore used to give an indication to another person.
   - Simple: A light, flag, or other device that shows a message to someone, often telling them to stop or go.
   - _The railway signal switched to green, allowing the express to proceed._
   - _The engineer slowed the train as soon as the signal beside the tracks turned from green to red._
5. A varying quantity or sequence of states, such as a changing voltage, that represents or carries information, especially in electronics and communications.
   - Simple: A changing amount or pattern, such as electric pulses, that carries information from one place to another.
   - _Scientists treated the faint variation in brightness as a signal worth analyzing._
   - _The sensor turns each change in pressure into a signal the computer can read._
6. A sign, indication, or action that shows something is the case or is about to happen, or that conveys information about someone's intentions or qualities.
   - Simple: Something that shows what is true, what someone intends, or what is likely to happen.
   - _The sudden drop in sales was an early signal of trouble ahead._
   - _A change in the birds' behavior can be a signal of approaching bad weather._
7. A signaling interaction between cells, by which one cell conveys information to another.
   - Simple: A message passed between cells to tell them what to do.
   - _A hormone acts as a signal that prompts nearby cells to respond._
   - _Researchers traced the signal that triggers the immune cells to attack._
8. Useful or meaningful information, in contrast to noise or random interference.
   - Simple: Useful information that stands out from all the random, useless background.
   - _Analysts struggled to separate the signal from the noise in the survey data._
   - _Most forum chatter is noise; the real signal comes from a few experienced users._

## Verb

3. To communicate something, or to tell someone to do something, by means of a sign, gesture, light, sound, or other signal.
   - Simple: To show or tell something, or tell someone to do something, using a sign, movement, light, or sound.
   - _A flashing light can signal danger to oncoming traffic._
   - _The committee voted to signal its support for the new policy._

## Adjective

9. Standing out above others in rank, importance, or achievement; remarkable or outstanding.
   - Simple: Much greater than usual in rank, importance, or success.
   - _Her work marked a signal achievement in cancer research._
   - _The treaty was a signal success for the new government._

## Other meanings

- (noun) A simple form of interprocess communication used to notify a process or thread that something has occurred.

## Origin

The word comes from Old French "segnal" or "seignal," or from Medieval Latin "signāle," a noun use of Late Latin "signālis," which traces back to Latin "signum" (sign). Its verb use dates from 1805, shortened from "signalize" (1650s).

Source: DictionaryAI, https://dictionaryai.com/define/signal (written from Wiktionary data, CC BY-SA 4.0: https://creativecommons.org/licenses/by-sa/4.0/).