This book is an authoritative account of multilingualism in the present era, a phenomenon affecting a vast number of communities, thousands of languages and millions of language users. The book's focus is specifically on the knowledge and use of multiple languages, but its treatment of the topic is very wide-ranging. It deals with both bilingualism and polyglottism, at the level of the individual speaker as well as at the societal level. The volume addresses not only linguistic facets of multilingualism but also multilingualism's cultural, sociological, educational, and psychological dimensions, moving from classic perspectives to recent and emerging directions of interest. The book's extensive coverage takes in topics ranging from the `new linguistic dispensation' in our globalized world to child development in multilingual environments, from the classification of multilingual groupings to characteristics of the multilingual mind. This breadth makes Multilingualism an ideal advanced textbook for undergraduate and postgraduate students in the areas of linguistics, education and the social sciences.