This short book is two books in one. First, it is a genuinely introductory introduction to the main concepts of Systemic Functional Grammar (SFG) for the 21st century. Drawing on recent research, it focusses on the structure of the clause in English, bringing out clearly the 'multifunctional' nature of language, and the way in which structures are the result of 'choices between meanings'. It is an 'extension' of Halliday's SFG in several ways, including the introduction of new elements that are of growing importance in the language, and a 'simplification' of it in that it shows how the many 'strands of meaning' in a clause can be expressed in a single structure. But this is also a book for experienced linguists (who may include the teachers of the first group) who are interested in a scholarly work which compares the two main current versions of Systemic Functional Grammar with respect to the structure of the English clause, and gives reasons for every decision to prefer one analysis