Book excerpt: This book defines engagement for the field of language learning and contextualizes it within existing work on the psychology of language learning and teaching. Chapters address broad substantive questions concerned with what engagement is or looks like, and how it can be theorized for the language classroom; methodological questions related to the design, measurement and analysis of engagement in language classrooms and beyond; as well as applied issues examining its antecedents, factors inhibiting and enhancing it, and conditions fostering the re-engagement of language learners who have become disengaged. Through a mix of conceptual and empirical chapters, the book explores similarities and differences between motivation and engagement and addresses questions of whether, how and why learners actually do exert effort, allocate attention, participate and become involved in tangible language learning and use. It will serve as an authoritative benchmark for future theoretical and empirical research into engagement within the classroom and beyond, and will be of interest to anyone wishing to understand the unique insights and contributions the topic of engagement can make to language learning and teaching.