This fourth edition of the best-selling Theories in Second Language Acquisition surveys the major theories and frameworks currently used in second language acquisition (SLA) research, serving as an ideal introductory text for graduate students in SLA and language teaching.Designed to provide a consistent and coherent presentation for those seeking a basic understanding of the theories and frameworks 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 fully revised edition is the incorporation of a new theoretical framework to replace several lesser-used theories.A key work in the study of second language acquisition, this volume will be useful to students of linguistics, language, and language teaching, and to researchers as a guide to theoretical work outside their respective domains.