母语 (mǔ yǔ): Mother tongue (Noun) — Meaning & Stroke Order

At the formal international conference, delegates are permitted to speak in their respective mother tongues.

Do you think that mother tongue proficiency affects the efficiency of learning a second language?

He grew up abroad from childhood, so his mother tongue is not Chinese but English.

Mastering one's mother tongue not only aids communication but also deepens the understanding of one's own culture.