Bilingualism
Bilingualism generally refers to the existence of more than one language in an individual or a community. Bilingualism in a broad meaning constitutes the most common condition on both the personal level and the society level: the real exception is rather monolinguism. More specifically, bilingualism refers to both the broader and more general concept of the knowledge and usage of two languages, and the more specific concept of linguistic inventory (better defined as social bilingualism) formed by two languages, which stands opposite to diglossia. Diglossia is therefore a particular form of bilingualism in which the two available languages are related in a hierarchical and complementary way.