What does signal mean?
A signal is something that communicates information, prompts an action, or draws attention to a possible event. People use signals in many forms: a raised hand, a flashing light, a warning siren, a change in a traffic light, or a message sent electronically. The word can also mean an indication that something is beginning or likely to happen, as in "a signal of economic recovery." In communications and computing, a signal is information represented or transmitted through a physical or digital system. Signal can function as a verb, meaning to communicate or indicate through a deliberate signal, and as an adjective meaning especially notable, a use particularly associated with British English in phrases such as "signal failure." Its broad range—from ordinary human gestures to advanced electronic transmission—makes it useful wherever communication, warning, interpretation, or technical transmission is being discussed.
An indication, warning, gesture, or transmitted message used to communicate information or prompt an action.
"The bright green light is a signal that the path is safe."
In technical contexts, a signal is an information-bearing electrical, electromagnetic, or digital transmission.
To communicate or indicate by means of a signal, or to give a signal to someone.
"The driver signalled to turn left."
Common in transport, communications, computing, and descriptions of deliberate human gestures.
Especially notable or conspicuous, often because something has conspicuously succeeded or failed.
"The expedition was a signal failure of planning."
This use is especially common in British English, particularly in expressions such as "signal failure" and "signal success."
The regular plural of the noun is "signals."
"The radio received several weak signals from the station."
Signal descends from the Latin signum, the same ancient root that gave us sign, signify, signature, and insignia.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does signal come from?
English borrowed signal from French, which continued the Medieval Latin adjective signalis, meaning "of or relating to a sign." That form derives from Latin signum, meaning "sign" or "token." The development connects signal with a wider family including sign, signify, signature, and insignia, all ultimately associated with marking, indicating, or identifying something.
Related word forms
How signal is actually used
The adjective is especially common in British usage, as in "a signal failure." In technical and scientific contexts, signal generally means information transmitted through a system, often contrasted with noise. As a verb, signal is widely used in transport, computing, communications, and everyday gestures.
Easily confused with signal
A sign is a visible or written marker, while a signal often actively conveys a message or is transmitted to communicate.