Pragmatics
Pragmatics[1] is the branch of linguistics concerned with language in use or the study of meaning as it arises from language occurring in context. Pragmatics does not examine the relationship between the word and its definition or sense (the domain of semantics) but the relationships between words and the entities (real-world or otherwise) to which those words refer (referents or discourse entities). Furthermore, the linguist working in pragmatics is trying to account for utterances in terms of the meaning intended by the speaker and understood by the hearer.
So for example, in semantics the utterance "I just got out of bed" would be analyzed for the meanings of the individual words as they occur in syntactic relation to each other. ("I" = first person pronoun, in subject position; "just" = adverb, indicating recency of action; etc.) In pragmatics, the utterance would be assessed in terms of its context. What particular person is the speaker ("I")? What does he intend the hearer to understand from his utterance? (Perhaps the speaker is declining an offer to go to the mall. None of the words spoken have the sense of "decline offer" or "mall", but in context the utterance would communicate that information -- in addition to communicating the merely semantic meaning of the sentence.)
In European linguistic circles, the field of pragmatics includes such disciplines as sociolinguistics and psycholinguistics, but in America pragmatics embraces a narrower field of inquiry (though exactly how narrow is a subject for debate among linguists).