Native Language

mother tongue, language one grew up speaking

The first language a human being learns to speak is his/her native language. He/She is a native speaker of this language according to Leonard Bloomfield A first language or native language is a basis for sociolinguistic identity.In linguistics first language can be referred to as arterial language, mother tongue, or L1.
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Noun
1. the language that a person has spoken from earliest childhood
(hypernym) language, linguistic communication

When used with reference to a person of limited English-speaking ability, means the language normally used by that person, or in the case of a child, the language normally used by the parents of the child. Bilingual Education Act.