mother tongue; native language
Ha comenzado a escribir el diccionario en su lengua materna.
He has begun writing the dictionary in his native language.
Ella habla inglés como si fuera su lengua materna.
She speaks English as if it were her native language.
Había olvidado que su lengua materna era el francés.
She had forgotten that her native language was French.
His native language is Russian.
Russian is his native language.
El francés es su lengua materna.
French is his native language.
El español es su lengua materna.
Spanish is his native language.
Uno debería amar su lengua materna.
One should love one's mother tongue.
Su lengua materna es el francés.
His native language is French.