Bilingualism (multilingualism) refers to the coexistence of more than one language system within an individual. Bilingualism is a product of extensive language contact. This book is a comprehensive source elaborating on the main concepts included under the term Bilingualism. The role of brain, environment as well as education in becoming a bilingual is meticulously discussed in different chapters of the present book. Plus, the theories of first and second language acquisition are thoroughly explained.