Investigations into ʻthe functions of languageʼ have often figured prominently in linguistic research; there are several possible reason for wanting to gain some insight into how language is used. Among other things, it would be helpful to be able to establish some general principles relating to the use of language; and this is perhaps the most usual interpretation of the concept of a functional approach.
- Halliday (1973), a pag.22

A fuctional approach to language means, first of all, investigating how language is used: trying to find out what are the purposes that language serves for us, and how we are able to achieve these purposes through speaking and listening, reading and writing. But it also means more than this. It means seeking to explain the nature of language in functional terms: seeing whether language itself has been shaped by use, and if so, in what ways – how the form of language has been determined by the functions it has evolved to serve.
- Halliday (1973), a pag.7