a declarative sentence can be used to perform a number of different speech acts. In uttering It's cold in here a speaker may perform an act of requesting the hearer to close the window or turn up the heating.

a communicative activity, defined with reference to what is said by the speaker, the intentions of the speaker while speaking, and the effects achieved on the listener.

Technical term in philosophy of language to refer to the different functions of language, e.g., locutionary, illocutionary, perlocutionary, constative, performative or, more simply, communicating, promising, commanding, naming, etc.

the use of language to perform some act

an utterance that serves a function in communication

an utterance that serves some function in communication

a unit of language that is produced in order to achieve a particular purpose, such as a command, question, reply, request, apology, complaint, etc

An action performed by the use of an utterance, in speech or writing, to communicate. [53

The theory of speech acts views natural language utterances as actions -- for example, questions, orders, statements -- on the part of speakers. Speech act theory belongs to the field of pragmatics.

The notion speech act is a technical term in linguistics and the philosophy of language. There are several different conceptions of what exactly "speech acts" are; following the usage of, for example, Peter F. Strawson and John R.