theory of signs the philosophical and scientific theory of information-carrying entities, communication, and information transmission. The term ‘semiotic’ was introduced by Locke for the science of signs and signification. The term became more widely used as a result of the influential work of Peirce and Charles Morris. With regard to linguistic signs, three areas of semiotic were distinguished: pragmatics – the study of the way people, animals, or machines such as computers use signs; semantics – the study of the relations between signs and their meanings, abstracting from their use; and syntax – the study of the relations among signs themselves, abstracting both from use and from meaning. In Europe, the near-equivalent term ‘semiology’ was introduced by Ferdinand de Saussure, the Swiss linguist.
Broadly, a sign is any information-carrying entity, including linguistic and animal signaling tokens, maps, road signs, diagrams, pictures, models, etc. Examples include smoke as a sign of fire, and a red light at a highway intersection as a sign to stop. Linguistically, vocal aspects of speech such as prosodic features (intonation, stress) and paralinguistic features (loudness and tone, gestures, facial expressions, etc.), as well as words and sentences, are signs in the most general sense. Peirce defined a sign as ‘something that stands for something in some respect or capacity.’ Among signs, he distinguished symbols, icons, and indices.
A symbol, or conventional sign, is a sign, typical of natural language forms, that lacks any significant relevant physical correspondence with or resemblance to the entities to which the form refers (manifested by the fact that quite different forms may refer to the same class of objects), and for which there is no correlation between the occurrence of the sign and its referent. An index, or natural sign, is a sign whose occurrence is causally or statistically correlated with occurrences of its referent, and whose production is not intentional. Thus, yawning is a natural sign of sleepiness; a bird call may be a natural sign of alarm. Linguistically, loudness with a rising pitch is a sign of anger. An icon is a sign whose form corresponds to or resembles its referent or a characteristic of its referent. For instance, a tailor’s swatch is an icon by being a sign that resembles a fabric in color, pattern, and texture. A linguistic example is onomatopoeia – as with ‘buzz’. In general, there are conventional and cultural aspects to a sign being an icon. See also GRAMMAR, MEANING, PHILOSOPHY OF LANGUAGE , SEMIOSI. W.K.W.