A signal is any variation of a medium that conveys information. Signal or signaling may refer to: Science and technology Analog signal Audio signal Digital signal Digital signal (signal processing) Cell signaling, in biology Signalling (economics), in economics theory Signalling theory, in evolutionary biology Time signal Computing SIGNAL (programming language), a synchronous programming language Signal (software), an end-to-end encrypted voice calling, video calling and instant messaging application Signal Protocol, a cryptographic protocol used by the Signal application Signal (IPC), a form of inter-process communication used in Unix and related operating systems C signal handling, a way for handling signals received by programs during their execution A term in functional reactive programming Communications International Code of Signals, a standard for sending signals by displaying flags Maritime flag signalling, generally flaghoist signalling, by which ships communicate with each other Naval flag signalling, covers various forms of flag signalling, such as semaphore or flaghoist Military communications, often called "signals" Recognition signal in human, technical or biological communications Signaling protocol to establish or tear down a connection, and to identify the state of the connection Signaling (telecommunications), a part of some communication protocols Smoke signal, an ancient form of communication Telegraphic signal, in telegraphy Transportation Railway signal Traffic light Arts and entertainment Signal (magazine), a Wehrmacht propaganda magazine which was published in occupied Europe during World War II SIGNAL (US magazine), publication of the Armed Forces Communications and Electronics Association Signal, a New York Yiddish-language literary monthly published from 1933 to 1936 by the Communist Party USA Signal (novel), a 2009 children's novel about a boy who helps a girl from another planet signal her parents Signal (South Korean TV series), a 2016 South Korean police procedural TV series Signal (Japanese TV series), a 2018 Japanese police procedural TV series based on the 2016 South Korean series of the same name Signal – The Southeast Electronic Music Festival, an annual music festival held in the US Signal, Wyoming, a fictional town from the 2005 film Brokeback Mountain "Signals", a 2005 episode of the animated television series 12 oz. Mouse Music Signal (band), a Bulgarian rock band Albums Signal (album), a 2005 album by Casiopea Signals (Mal Waldron album), 1971 Signals (Mallory Knox album), the début album of the Mallory Knox band Signals (Rush album), 1982 Signals (Wayne Krantz album), 1990 Signals, an album by American band Devour the Day Signal (EP), a 2017 extended