Written for students encountering the topicthe first time, this is a clear and practical introduction to second language acquisition (SLA). Using non-technical language, it explains how asecond language is acquired, what the learner of a second language needs to know, and why some learners are more suceessful than others. This new edition of Muriel Saville-Troike´s bestselling textbook introduces in a step-by-step fashion a range of fundamental concepts, such as SLA in adults and children in formal and informal learning contexts, and in diverse socio-cultural settings. Taking an interdisciplinary approach, it encourages students to consider SLA from linguistic, psychological, and social perspecticves. Providing a solid foundation in SLA, this book has become the leading introduction to the field for students of linguistics, psychology, and education, and trainee language teachers.