Michael Halliday

Halliday (1970) introduced systemic functional linguistics, a model for analysing the language in terms of the interrelated systems of choices that are available for expressing meaning. The term systemic is used because whenever a feature of language is described it is described as one choice from a set of all possible choices within a particular language system that make up the language as a whole. Language users are constantly making choices from the set of systems and then putting these choices int effect through the structure of the language they use. Linguists use system diagrams to map the way the language users make choices as they move through hierarchy of language systems, and finally apply their choices in language structures.