In [[linguistics]], a sentence '''function''' refers to a speaker's purpose in uttering a specific sentence, phrase, or clause. Whether a listener is present or not is sometimes irrelevant. It answers the question: "Why has this been said?" The fourfive 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: from https://www.ucl.ac.uk/internet-grammar/clauses/discours.htm)
