This book provides a clear introduction to first and second language acquisition. It not only offers definitions and theoretical backgrounds but also a range of practical tips for sensitively dealing with bilingualism in school and family settings. New in this revised and expanded edition is a chapter on German language support for refugee children. Additionally, the chapter on "foreign language" has been updated with current scientific and educational policy insights and changes. As in the previous edition, the book thoroughly presents the central concepts of communication and language and explains the various hypotheses regarding the acquisition of first, second, and foreign languages. Based on this foundation, it outlines concrete possibilities for diagnosis and support for daily practice. The new chapter on German language support for refugee children explains the challenges.