signal

"Signal" is a very useful word in English with around 4 common meanings. It can be a noun, a verb, or even an adjective. At its heart, it is always about communication — sending a message or a sign to someone or something.

1nouna sign or gesture that communicates something

A signal is any action, sound, light, or movement that sends a message to someone. Think of it as a way of saying something without necessarily using words. A red traffic light is a signal to stop. A wave of the hand is a signal to say hello or goodbye.

everyday language · Modern, widely used

The referee blew the whistle as a signal for the game to begin.

She gave him a signal by nodding her head to show she was ready.

The smoke was a signal that someone was in the cabin.

2nouna radio, TV, or phone transmission

In technology, a signal is the invisible wave that carries information — like sound, images, or data — from one device to another. When your phone has 'no signal', it means it cannot connect to the network to send or receive calls and messages.

technology / telecommunications · Modern, widely used

My phone has no signal in this part of the building.

The radio signal was too weak to pick up the station clearly.

Satellites send signals back to Earth to provide GPS navigation.

3verbto make a gesture or sign to communicate

When you signal, you use an action, a light, or a sound to tell someone something. For example, a driver signals before turning by using the car's indicator lights. You can also signal with your body — like raising your hand to get a waiter's attention.

everyday language · Modern, widely used

He signalled to the taxi driver to stop.

The teacher signalled for the students to be quiet by raising her hand.

Always signal before you change lanes when driving.

4verbfigurativeto indicate or suggest something

You can also use 'signal' to mean that something is a sign or a clue that another thing is happening or about to happen. For example, dark clouds signal that rain is coming. Here, the clouds are not literally sending a message — they just tell us something important.

everyday language / journalism · Modern, widely used · figurative

The drop in temperature signalled the arrival of winter.

His silence signalled that he was not happy with the decision.

The new policy signals a major change in the company's direction.

5adjectivefigurativeremarkable or very important

As an adjective, 'signal' means something is very notable or significant. This use is quite formal and you will mostly see it in written or older texts. For example, a 'signal achievement' is an outstanding, impressive achievement.

formal writing / literature · Formal, more common in older texts · figurative

Winning the championship was a signal moment in her career.

The discovery of penicillin was a signal achievement in medical history.

He made a signal contribution to the field of mathematics.