Now in its second edition, this highly accessible introductory textbook establishes the fundamentals driving the field of second language (L2) acquisition research, including its historical foundations. Intended for the novice in the field with no background in linguistics or psycholinguistics, it explains important linguistic concepts, and how and why they are relevant to second language acquisition. Topics are presented via a 'key questions' structure that enables the reader to understand how these questions have motivated research in the field, and the problems to which researchers are seeking solutions. This edition has been fully updated to incorporate new research, with a new chapter focusing on language transfer, and new sections on the growing field of third and subsequent language acquisition, and how phonology interacts with L2 acquisition. With discussion questions and project ideas as well as a glossary, this is a complete package for an introductory course on second language acquisition.