Bilingualism Definition

First / Second Language

The mother tongue, L1, or first language all refer to the language first learned by a child during development. It is the language of communication used with the child before it learns to speak. In child development, language acquisition extends generally from 0 to 3 years. A language learned after the age of 12 is regarded as a second language designated L2.

First Language Acquisition

In the bilingual “first language acquisition” ("natural" simultaneous learning of two languages), there are different constellations.

1. 
   A family language (L1), an environment language (L2) (kindergarten, outside world).
   
2. 
   Mixed-languages families A (father speaks L1, mother speaks L2, the environment speaks L1 or L2).
   
3. 
   Mixed-languages families B (father speaks L1, mother speaks L2) in a different-language environment (L3).