This book is intended for readers who seek information on issues related to plurilingualism and the integration of subject content teaching with additional languages such as heritage, autochthonous, regional and foreign languages that are taught in school contexts. The book provides information on recent theoretical and pedagogical paradigm shifts in applied linguistics and highlights the links between research, theory and pedagogy. It provides a comprehensive review of concepts and epistemologies related to AL pedagogies and plurilingualism. The last part of the book presents various interaction types used in AL classrooms and proposes interaction analysis as a research method and teacher education tool.