Sentence function

In linguistics, a sentence function refers to a speaker's purpose in uttering a specific sentence, clause, or phrase. Whether a listener is present or not is sometimes irrelevant. It answers the question: "Why has this been said?" The five basic sentence forms (or "structures") in English are the declarative, interrogative, exclamative, imperative and the optative. These correspond to the discourse functions statement, question, exclamation, and command respectively. The different forms involve different combinations in word order, the addition of certain auxiliaries or particles, or other times by providing a special form. There is no clear one-to-one correspondence between the forms/structures and their discourse functions. For example, a declarative form can be used to ask a question, and interrogative form can be used to make a statement.

For instance, the following sentence has declarative form:

You need some help

But when this is spoken with a rising intonation, it becomes a question:

You need some help?

Conversely, rhetorical questions have the form of an interrogative, but they are really statements:

Who cares? ( = I don't care)

The four main categories can be further specified as being either communicative or informative, although this is somewhat simplistic.