In semiotics, a sign is generally defined as, "...something that stands for something else, to someone in some capacity. It may be understood as a discrete unit of meaning, whether denotative or connotative. Signs are not just words, but also include images, gestures, scents, tastes, textures, sounds — essentially all of the ways in which information can be processed into a codified form and communicated as a message by any sentient, reasoning mind to another.

Initially, within linguistics and later semiotics, there were two general schools of thought: those who proposed that signs are dyadic, and those who proposed that signs are interpreted in a recursive pattern of triadic relationships.