In linguistics and philosophy of language, an utterance is felicitous if it is pragmatically well-formed. An utterance can be infelicitous because it is self-contradictory, trivial, irrelevant, or because it is somehow inappropriate for the context of utterance. Researchers in semantics and pragmatics use felicity judgments much as syntacticians use grammaticality judgments. An infelicitous sentence is marked with the pound sign.