A sign is an entity which indicates another entity. Sign may also refer to: Communication Signage, the use of signs and visual graphics to convey information Signature, a handwritten depiction of someone's name or other mark used as a proof of identity and intent Sign (semiotics), anything that communicates a meaning Sign language, a languages that uses the visual-manual modality to convey meaning Mathematics Sign (mathematics), an indication of negative and positive numbers Sign function, also known as the signum function Sign of a permutation of a finite set Organizations Project Sign, a project by the U.S. Air Force to investigate unidentified flying objects (UFOs) Servicio de Inteligencia de la Gendarmería Nacional or Inteligencia de la Gendarmería Nacional Argentina, the Argentine intelligence service Scottish Intercollegiate Guideline Network, a Scottish group that develops evidence-based medical guidelines Music Sign (band), an Icelandic band Sign (Clock DVA album), 1993 "Sign" (Mr. Children song), 2004 "Sign" (Beni Arashiro song), 2010 "Sign" (Flow song), 2010 "Sign", a 2018 song by Exo from Don't Mess Up My Tempo "Sign", a 2001 song by Marcella Detroit from Dancing Madly Sideways "Sign", a song by Susumu Hirasawa "Sign-2", a different version of "Sign" from Berserk: Millennium Falcon Hen Seima Senki no Shō Sign (Autechre album), 2020 "The Sign" (song), a 1993 song by Ace of Base The Sign (Ace of Base album), a 1993 album by Ace of Base Surname Christopher Sign (19762021), American journalist Other uses Astrological sign, one of twelve sectors of the sky in astrology Medical sign, an indication of disease, injury, or abnormal physiological state Sign (TV series), a 2011 South Korean television series See also Signs (disambiguation) Signing (disambiguation) Sign-Trace Sine, a trigonometric function of an angle Sine (disambiguation)