Charles Sanders Peirce: Symbolic, Iconic, and Indexical Signs


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Road signs are symbols with meaning. Image by Lesley Lanir

Charles Sanders Peirce (1839–1914) formulated the innovative triadic model of the sign, emphasizing in his theory that the way we interpret a ‘sign’ is what allows it to be signified – what gives it its meaning.

Therefore, the main attributes of any sign need to be clear enough to relay their intended meaning.

What is a Sign?

Peirce’s theory does not focus on just material or concrete signs, but any kind of sign. For example, if a bus driver announces that the next stop is Central Station and a passenger rings the bell, lighting up the ‘stop’ sign  – then the sign system here has been understood.

The message contained  in the driver’s announcement is the sign that he will drive straight past that terminal if noone responds. His announcement is Peirce’s ‘representamen’ or Saussure’s ‘signifier.’ How the passengers react is the ‘interpretant’ or ‘signified’, or sense made of the sign.

If the driver stops or carries on, that is the referent, the object of the sign. A passenger rings the bell and the stop sign lights up – the driver’s ‘sign’ has been understood.

The driver interprets the sound of the bell as representing a sign informing him he must stop. The other passengers on the bus understand this, too, from the sound of the bell and the lighted sign. Both represent that the bus will stop – the object of the sign.

Peirce’s Three Sign Modes

We are surrounded by an infinite number of signs. Peirce understood this and offered many different principles for how to categorize them according to their three triadic elements:  representamen, object and intrepretant.

He proposed that signs could be classified according to the qualities, facts, laws and conventions associated with the objects. This way of tabulating signs led to ten different sign types.

By examining the relationship between objects, interpretants, and representamens and, in particular, the way the referent determines the sign, Peirce also distinguished three main ‘modes’  into which signs can be assigned: symbol, icon and index.

Index signs are easier to understand and more commonly used.

Symbol or Symbolic Sign

In this mode, the symbol or symbolic sign is assigned arbitrarily or is accepted as societal convention. Therefore, the relationship between the representamen and what the sign stands for – its object or referent and the sense behind it, the interpretant – must be learned. For example, letters of the alphabet, the number system, mathematical signs, computer code, punctuation marks, traffic signs, national flags and so forth.

Iconic paintings have meaning as well as aesthetic value. Image by Lesley Lanir

Icon or Iconic Sign

As an icon, the representamen resembles or imitates its signified object in that it possesses some of its qualities. Therefore, the relationship between what the sign stands for – its referent and the sense behind it, the interpretant  –  does not necessarily have to be learned. For example, a portrait, a cartoon, sound effects, or a statue.

Are tire tracks indexical signs, icons or symbols? Image by Lesley Lanir

Index or Indexical Sign

An index is a  mode in which the signifier might not resemble its signified object. It is not arbitrarily assigned and is directly connected in some way to the object. Nevertheless, the relationship between what the sign stands for – its referent and the sense behind it, the interpretant – may have to be learned.
The link between the  representamen and its object may only be inferred; for instance, smoke, thunder, footprints, flavors, a door bell ringing, or a photograph, film or DVD recording.

Symbol, Icon or Index?

The three modes have different levels of conventionality, predictability and conformity.  For example, symbols such as letters and numbers are usually highly conventional. The system is determined, fixed and understood. Iconic signs usually have some degree of conventionality, and indexical signs, according to Peirce’s writings, can ‘direct the attention to their objects by blind compulsion.’

The indirect links between icons and indices suggest that a referential context exists outside the sign-system and, as Peirce emphasized, the three forms are not necessarily mutually exclusive. For Peirce, semiotics was a process of understanding and not a structured system, so a sign under this model can be perceived as an icon, symbol or index, or a combination of the three depending on its use and interpretation.


Peirce, C.  Collected Writings (8 Vols.). (1931-58). Ed. Charles Hartshorne, Paul Weiss & Arthur W Burks. Cambridge, MA: Harvard University Press.

Atkin, A. Peirce’s Theory of Signs. (2010). The Stanford Encyclopedia of Philosophy. Edward N. Zalta (ed.). Accessed December  29, 2012.

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