This third edition of the best-selling Theories in Second Language Acquisition surveys the major theories currently used in second language acquisition (SLA) research, serving as an ideal introductory text for undergraduate and graduate students in SLA and language teaching. Designed to provide a consistent and coherent presentation for those seeking a basic understanding of the theories that underlie contemporary SLA research, each chapter focuses on a single theory. Chapters are written by leading scholars in the field and incorporate a basic foundational description of the theory, relevant data or research models used with this theory, common misunderstandings, and a sample study from the field to show the theory in practice. New to this edition is a reduction of the original preliminary chapters, the elimination of a chapter reviewing the various theories and what they explain, and the addition of a chapteraddressing the relationship between theories and L2 teaching.A key work in the study of second language acquisition, this book will be useful to students of linguistics, language and language teaching, and to researchers as a guide to theoretical work outside their respective domains.