This updated and revised edition of Hamers and Blanc's successful textbook presents state-of-the-art knowledge about languages in contact from individual bilingualism (or bilinguality) to societal bilingualism. It is both multi- and interdisciplinary in approach, and analyses bilingualism at individual, interpersonal, and societal levels. Linguistic, cognitive and sociocultural aspects of bilingual development are explored, as are problems such as bilingual memory and polyglot aphasia. Hamers an