This book brings together two approaches to the description of language: Systemic Functional Linguistics (SFL) and Corpus Linguistics (CL). SFL is essentially a theory of language; CL is essentially a method for investigating language. Yet this dichotomy between theory and practice is too simplistic. As shall be discussed below, SFL is increasingly concerned with methods of quantifying linguistic features, and CL is becoming more intent on developing theories to account for its findings. Many practitioners, whatever their backgrounds, have a sympathy for both approaches and see them as complementary rather than in opposition. On the other hand, there are differences which are worth exploring rather than glossing over. This book explores the synergy between the two approaches, celebrating complementarities and articulating points of disparity. It is our belief that this exploration will benefit both SFL and CL, and will constitute a contribution to all ‘usage based’ models of language (Barlow and Kemmer 2000).