This volume provides a definitive view of the relationship between input, interaction, and second language acquisition. In so doing, it should prove useful to those whose major concern is with the acquisition of a second or foreign language as well as for those who are primarily interested in these issues from a pedagogical perspective. The book does not explicate or advocate a particular teaching methodology, but does attempt to lay out some of the underpinnings of what is involved in interaction -- what it is and what purpose it serves. Research in second language acquisition is concerned with the knowledge that second language learners do and do not acquire and how that knowledge comes about. This book ties these issues together from three perspectives -- input/interaction framework, information-processing, and learnability.