This major new textbook offers an accessible introduction to many of the most interesting areas in the study of multilingualism. It consists of twelve lectures, written by leading researchers, each dedicated to a particular topic of importance. Each lecture offers a state-of-the-art, authoritative review of a subdiscipline of the field. The volume sheds light on the ways in which the use and acquisition of languages are changing, providing new insights into the nature of contemporary multilingualism. It will be of interest both to undergraduate and postgraduate students working in linguistics-related disciplines and students in associated social sciences.