This volume brings together empirical research that explores interaction in a wide range of educational settings. It includes work that takes a cognitive, brain-based approach to studying interaction, as well as studies that take a social, contextual perspective. Interaction is defined quite broadly, with many chapters focusing on oral interaction as is typical in the field, while other chapters report work that involves interaction between learners and technology. Several studies describe the linguistic and discourse features of interaction between learners and their interlocutors, but others demonstrate how interaction can serve other purposes, such as to inform placement decisions. The chapters in the book collectively illustrate the diversity of contemporary approaches to interaction research, investigating interactions with different interlocutors (learner-learner, learner-teacher), in a variety of environments (classrooms, interactive testing environments, conversation groups) and through different modalities (oral and written, face-to-face and technology-mediated).