Relevance theory is a framework for understanding the interpretation of utterances. It was first proposed by Dan Sperber and Deirdre Wilson, and is used within cognitive linguistics and pragmatics. The theory was originally inspired by the work of Paul Grice and developed out of his ideas, but has since become a pragmatic framework in its own right. The seminal book, Relevance, was first published in 1986 and revised in 1995.
The theory takes its name from the principle that "every utterance conveys the information that it is relevant enough for it to be worth the addressee's effort to process it", that is, if I say something to you, you can safely assume that I believe that the conveyed information is worthwhile your effort to listen to and comprehend it; and also that it is "the most relevant one compatible with the communicator's abilities and preferences", that is, I tried to make the utterance as easy to understand as possible, given its information content and my communicative skills.
Other key ingredients of relevance theory are that utterances are ostensive (they draw their addressees' attention to the fact that the communicator wants to convey some information) and inferential (the addressee has to infer what the communicator wanted to convey, based on the utterance's "literal meaning" along with the addressee's real-world knowledge, sensory input, and other information).
Inferences that are intended by the communicator are categorised into explicatures and implicatures. The explicatures of an utterance are what is explicitly said, often supplemented with contextual information: thus, "Susan told me that her kiwis were too sour" might under certain circumstances explicate "Susan told the speaker that the kiwifruit she, Susan, grew were too sour for the judges at the fruit grower's contest". Implicatures are conveyed without actually stating them: the above utterance might for example implicate "Susan needs to be cheered up" and "The speaker wants the addressee to ring Susan and cheer her up".
Relevance theory also attempts to explain figurative language such as hyperbole, metaphor and irony.
Critics have stated that relevance, in the specialised sense used in this theory, is not defined well enough to be measured. Other criticisms include that the theory is too reductionist to account for the large variety of pragmatic phenomena.