The Ultimate Sign - American History Information Guide and Reference

Sign can denote any of the following:

Within a writing system, a sign is a basic unit. Similar terms which are more specific are character, letter or grapheme.
Signs are the basic units of semiotics, which is the systematic study of signs.
In linguistics, Ferdinand de Saussure described a sign as a combination of a concept and a sound-image.
In medicine, a sign is objective evidence of the presence of a disease or disorder, as opposed to a symptom, which is subjective.
In computing, the digits where one bit among them tells the number is either negative or non-negative are called signed, otherwise unsigned. See also: Signedness
In mathematics, the sign of a number refers to whether it is negative or positive.
On (the side of or above) roads there are traffic signs to instruct drivers. In most parts of the world these include stop signs, speed limit signs, cross walk signs, and others.
Information signs are notices that instruct, advise, inform or warn people.
In Astrology sign is often used to mean the Sun sign.
In communication sign or signing refers to communicating via hand gestures, such as sign language.

Your American History Reference Guide! - Sign