Halliday's functional grammar is a unique way of describing how language is actually used in a social situation. This is not a grammar of rules, but rather an analysis of language and its functions.

Tom and Meriel Bloor's book is the best introduction to this grammar. Written as a course textbook, with a clear, methodical presentation and exercises, it can also be read as a general introduction for the curious. It is complete and highly readable, and the grammatical theories it presents and explains can be useful to anyone who works with language, to better understand how language works. Language is not examined here out of context - in fact, context is one of the key factors in Halliday's grammar - rather, Bloor and Bloor show how isolated bits of text fit in with the larger perspective of language as a whole.