When we wish to speak of our "good friend or friends," in our enlightened tongue, we stick to the one form and have no trouble or hard feeling about it; but with the German tongue it is different.

当我们想说我们的“好朋友(们)”时，只有一种形式，简单明了；到了德语里，可大相径庭了。

youdao

Her lapse into German didn't seem peculiar. After all, it was her native tongue.

她开始说德语并不奇怪，毕竟那是她的母语。

《柯林斯英汉双解大词典》

His mother tongue was German and at school he learned French and English, but he felt his English was poor.

他的母语是德语，在学校学了法语和英语，但他觉得自己的英语很差。

youdao

Most speak neither German nor their mother tongue well, says Volker Steffens, the school's principal.

ECONOMIST: Germany's Turkish minority

Safety instructions are screamed at you in four languages Dutch, English, French and German each spoken with such a terrible accent that one wonders if the flight attendants have a mother tongue at all.

ECONOMIST: Sweden's model economy