Language is used to do a wide range of activities. These activities are called speech acts . The three major uses of language are reflected in declarative, interrogative, and imperative sentences, used in statements, questions, and commands.
Felicity conditions refer to the situational appropriateness of an utterance.
When people interact, certain assumptions are made. In questioning, the assumptions are that the questioner does not know the answer, the questioner wants to know the answer, and that the questioner believes that the listener may be able to help. In requests, the assumptions are that the job has yet been done, that the requester believes that the listener can do the job, that the listener is willing to do the job, and that the requester wants the job to be done. These felicity conditions are the key to indirect speech acts. In an indirect speech act , the speaker means something different from what he literally says.