复返

qù ér fù fǎn

去而复返

go and come back

tā yī qù bù fù fǎn

他一去不复返。

He has gone, never to return.

huān lè hé xī xì de rì zi yī qù bù fù fǎn

欢乐和嬉戏的日子一去不复返。

The days of fun and frolic were gone for ever.