Research on language contact deals with how languages mutually influence each other in multilingual societies or among multilingual individuals. This involves the dynamics of linguistic systems and processes of change, as well as socio- and psycholinguistic questions. The introduction provides a comprehensive overview of the various approaches, methods, and foundations of this field of research. It describes the effects of language contact and the phenomena at the linguistic surface in a simple, easily readable manner. The third, revised edition takes into account current research approaches and developments.