母国語

Etymology
Compound of.

Noun

 * 1) the language of the country of one's birth
 * 2) native language, mother tongue, first language

Usage notes
In common Japanese usage, this term is synonymous with. However, bokokugo and bogo may refer to different things, such as in the context of a country with more than one language (such as or ), or in the context of someone having moved to a different country.