mother tongue
US /ˈmʌð.ər ˌtʌŋ/
UK /ˈmʌð.ər ˌtʌŋ/

名詞
1.
母語, 母国語
the language that a person has grown up speaking from childhood; the native language of a person or a group of people
例:
•
English is my mother tongue, but I also speak French fluently.
英語は私の母語ですが、フランス語も流暢に話せます。
•
Learning a new language is easier if you have a strong foundation in your mother tongue.
母語にしっかりとした基礎があれば、新しい言語を学ぶのはより簡単です。
Lingolandでこの単語を学ぶ