Relevance is a relative notion. It is determined by two factors: contextual effect and processing effort. The greater the contextual effect, the greater the relevance. Processing effort is a negative factor: the greater the processing effort, the lower the relevance.

In verbal communication, the speaker must the hearer’s attention. To succeed, the communicator necessarily chooses the most relevant utterance from a range at his/her disposal that fits best to the context, the one that will call for the least processing effort.

The theory of relevance accounts for the fact that implicature and cooperation are not incompatible.