This edited volume has been compiled in honour of Professor Merrill Swain, one of the most prominent scholars in the field of second language acquisition (SLA) and second language (L2) education. For over four decades, her work has contributed substantially to the knowledge base of the field of applied linguistics, and her ideas have had a significant influence in a range of subfields, including immersion education, mainstream SLA, and sociocultural theory and SLA. The range of topics covered in the book reflects the breadth and depth of Swain’s contributions, expertise and interests. The volume is divided into four parts: immersion education, languaging, sociocultural perspectives on L2 teaching and learning, and developments in language as social action.