Signal, signals or signalling may refer to:

Scientific concepts

• Signal (electrical engineering), a varying quantity that can carry information
• Signal processing, the field of techniques used to extract information from signals
• Signal (computing), an event, message, or data structure transmitted between computational processes
• Signals (biology), electrochemical activity in an organism

Communications

• traffic signals in various kinds of transport:
  • railway signal
  • Semaphore (communication)
  • Beacon
  • International maritime signal flags, using the International Code of Signals
• signals (military), a historical name for the military communications
• Signalling theory in biology, how organisms signal their state to others
• Distress signal
• Smoke signal (See also Category:Early telecommunications)
• Signalling (telecommunications), a part of some communication protocols

Names

• Signal (band), a Bulgarian rock band
• Signals (Scottish Indie Band)
• Signals (album), an album by progressive rock band Rush
• Signal (magazine)
• Signal (toothpaste)
• Signal 1 and Signal 2 radio stations
• Signal (subscription service), service that provided real-time stock quotes
• Signaal (now Thales Nederland), a Netherlands based defence company

Other

• Any implicit, subtle, or disguised message, in situations such as:
  • Partnership card games (see signal (bridge))
  • Signaling (economics)
• Signals and slots, a software design pattern

إشارة | Signal | Signal | señal | Signal | signaal | 信号 | Sygnał