Susan M. Gass's *Input, Interaction, and the Second Language Learner* is a foundational text in the field of second language acquisition (SLA). This new edition, part of the Routledge Linguistics Classics series, includes the original text and a preface featuring consultations with Alison Mackey, Rod Ellis, and Mike Long, reflecting on the significance of the project two decades later. The book provides a comprehensive view of the relationship between input, interaction, and SLA, making it useful for both researchers and educators. It does not advocate a specific teaching methodology but explores the underlying principles of interaction, including what it is and how it serves its purpose. The book ties together research on SLA by examining three perspectives: the input/interaction framework, information processing, and learnability. The preface includes a conversation with Alison Mackey, who discusses her early interest in interaction and the development of the interaction approach. She highlights key milestones in the field, such as the work of Michael Long and Merrill Swain, and the evolution of the interaction hypothesis into a more comprehensive approach. The conversation also touches on the relationship between interactionist research and Task-Based Language Teaching (TBLT), noting the need for more research on classroom interactions and individual differences. The book's content covers various aspects of SLA, including modeling second language acquisition, the nature and function of output, input theories, the role of interaction, and the creation of learner systems. It concludes with a discussion on classroom implications and applications, emphasizing the importance of understanding how interaction facilitates learning. Overall, *Input, Interaction, and the Second Language Learner* remains a crucial resource for SLA scholars and students, offering insights into the complex interplay between input, interaction, and language learning.Susan M. Gass's *Input, Interaction, and the Second Language Learner* is a foundational text in the field of second language acquisition (SLA). This new edition, part of the Routledge Linguistics Classics series, includes the original text and a preface featuring consultations with Alison Mackey, Rod Ellis, and Mike Long, reflecting on the significance of the project two decades later. The book provides a comprehensive view of the relationship between input, interaction, and SLA, making it useful for both researchers and educators. It does not advocate a specific teaching methodology but explores the underlying principles of interaction, including what it is and how it serves its purpose. The book ties together research on SLA by examining three perspectives: the input/interaction framework, information processing, and learnability. The preface includes a conversation with Alison Mackey, who discusses her early interest in interaction and the development of the interaction approach. She highlights key milestones in the field, such as the work of Michael Long and Merrill Swain, and the evolution of the interaction hypothesis into a more comprehensive approach. The conversation also touches on the relationship between interactionist research and Task-Based Language Teaching (TBLT), noting the need for more research on classroom interactions and individual differences. The book's content covers various aspects of SLA, including modeling second language acquisition, the nature and function of output, input theories, the role of interaction, and the creation of learner systems. It concludes with a discussion on classroom implications and applications, emphasizing the importance of understanding how interaction facilitates learning. Overall, *Input, Interaction, and the Second Language Learner* remains a crucial resource for SLA scholars and students, offering insights into the complex interplay between input, interaction, and language learning.