Halliday's grammar differs markedly from traditional accounts that emphasise classification of individual words (e.g. noun, verb, pronoun, preposition) in formal, written sentences in a restricted number of "valued" varieties of English. Halliday's model conceives grammar explicitly as how meanings are coded into wordings, in both spoken and written modes in all varieties and registers of a language. Three strands of grammar operate simultaneously. They concern: (i) the interpersonal exchange between speaker and listener, and writer and reader; (ii) representation of our outer and inner worlds; and (iii) the wording of these meanings in cohesive spoken and written texts, from within the clause up to whole texts. Notably, the grammar embraces intonation in spoken language. Halliday's seminal "Introduction to Functional Grammar" (first edition, 1985) spawned a new research discipline and related pedagogical approaches. By far the most progress has been made on English, but the international growth of communities of SFL scholars has led to the adaptation of Halliday's advances to some other languages.