He misses his mum.

他想念他的妈妈。

Mum and Dad are coming for lunch.

爸爸和妈妈要来吃午饭。

Don't worry, Mum.

妈妈，别担心。

You're about to become a mum.

你要当妈妈了。

He is keeping mum about his feelings on the matter. [+ about]

他闭口不谈他对此事的个人感受。