This article critically examines the literature around grammar and grammatical terminology. It is essentially a critical consideration of the debates in England and Wales in four main parts. Part 1 considers debates in policy, the "What", i.e. grammatical terminology from the perspective of national policy as defined by the English National Curriculum for Key Stages 1 and 2, and the Key Stage 2 "Grammar, Punctuation and Spelling Test". Part 2, Debates in Purpose, examines the "Why": it views grammatical terminology through a more theoretical lens which considers the potential purpose and value of explicit grammatical terminology in the classroom. Part 3 touches upon Debates in Practice, the "How", examining what is already understood about the teaching of grammatical terminology in terms of grammar pedagogy, language acquisition and word learning. While each part has a distinct focus, the field is complex with overlap and interrelated issues. The final part looks briefly at teacher and pupil perspectives.