First language and Lingua franca

First language noun - One's native language; the language learned by children and passed from one generation to the next.

Lingua franca and first language are semantically related. In some cases you can use "Lingua franca" instead a noun phrase "First language".

Lingua franca noun - A common language used by speakers of different languages.

First language and lingua franca are semantically related. You can use "First language" instead a noun phrase "Lingua franca".