1. A motion or gesture by which a thought is expressed or a command or wish made known; signal; a fundamental linguistic unit that designates an object or relation or has a purely syntactic function; one of a set of gestures used to represent language; also; sign language
2. A mark having a conventional meaning and used in place of words or to represent a complex notion
3. One of the 12 divisions of the zodiac
4. A character (as a flat or sharp) used in musical notation; segno; a character indicating a mathematical operation; also; one of two characters + and - that form part of the symbol of a number and characterize it as positive or negative
5. A display (as a lettered board or a configuration of neon tubing) used to identify or advertise a place of business or a product; a posted command, warning, or direction; signboard
6. Something material or external that stands for or signifies something spiritual; something indicating the presence or existence of something else; presage, portent; an objective evidence of plant or animal disease

1. Cross; to place a sign on or mark by signs; to represent or indicate by a sign
2. To affix a signature to; ratify or attest by hand or seal; to assign or convey formally; to write down (one's name); to affix one's name to
3. To communicate by making a sign or by sign language
4. To engage or hire by securing the signature of on a contract of employment — often used with up or on
5. To write one's name in token of assent, responsibility, or obligation
6. To make a sign or signal; to use sign language

The character used to indicate a positive or negative number. In assembly-level programming, the sign is indicated by the sign bit accompanying the number. See also sign bit.