A sign is something that stands for something else to an interpreter.

This is Peirce’s formulation, and it is more careful than it sounds. The sign relation is triadic: it involves the sign itself (the representamen), the object the sign stands for, and the interpretant — the meaning produced in the interpreter by the sign. Without all three, there is no sign: a mark without an interpreter produces no meaning, and a meaning without a mark is not yet communicable (Peirce, 1931–1958).

The interpretant is the crucial third term. It is the functional effect the sign produces — the sign’s “meaning” in the sense of what it does, what it allows the interpreter to do or infer or feel. The interpretant is itself a sign (of the same object), which is why Peirce’s semiotics is intrinsically dynamic: signs generate interpretants that are themselves signs that generate further interpretants, producing an open-ended chain of semiosis (Short, 2007).

Types of signs

Peirce classified signs in multiple intersecting ways. Three basic types by the relation between sign and object:

  • icon: resembles its object (a portrait, a diagram)
  • Index: is causally or spatially connected to its object (smoke indexing fire, a finger pointing)
  • symbol: is connected to its object by convention (most words)

Source: Peirce, Charles Sanders. Collected Papers. Harvard University Press, 1931–1958. See also Short, T. L. Peirce’s Theory of Signs. Cambridge University Press, 2007.

Peirce, C. S. (1931–1958). Collected Papers of Charles Sanders Peirce (C. Hartshorne & P. Weiss, Eds.). Harvard University Press.
Short, T. L. (2007). Peirce’s Theory of Signs. Cambridge University Press.