Semiotics is the study of signs. It is an interdisciplinary field that examines what signs are, how they form sign systems, and how individuals use them to communicate meaning. Its main branches are syntactics, which addresses formal relations between signs, semantics, which addresses the relation between signs and their meanings, and pragmatics, which addresses the relation between signs and their users. Semiotics is related to linguistics but has a broader scope that includes nonlinguistic signs, such as maps and clothing.
Signs are entities that stand for something else, like the word cat, which stands for a carnivorous mammal. They can take many forms, such as sounds, images, written marks, and gestures. Iconic signs operate through similarity. For them, the sign vehicle resembles the referent, such as a portrait of a person. Indexical signs are based on a direct physical link, such as smoke as a sign of fire. For symbolic signs, the relation between sign vehicle and referent is conventional or arbitrary, which applies to most linguistic signs. Models of signs analyze the basic components of signs. Ferdinand de Saussure's dyadic model identifies a perceptible image and a concept as the core elements, whereas Charles Sanders Peirce's triadic model distinguishes a sign vehicle, a referent, and an effect in the interpreter's mind.