heritage language

noun2

1. •
   The language of one's ancestors, especially a language one would like to learn.

   • "I thought it was important for the American children to learn their heritage language," Palumbo said. — 1973
2. •
   A minority language that one acquires as a first language but uses and/or is exposed to less later in life in favor of a more dominant majority language.

   • Spanish is considered a heritage language in the United States.