3 sentences for 背 (bèi — hide)

1. 他背着妻子存了一点私房。

   tā bèi zhe qī​zi cún le yī​diǎn sī​fáng.

   He saved some private money behind his wife's back.

   Source: Dong Chinese Dictionary

2. 他背着妻子在外面和人勾搭。

   tā bèi zhe qī​zi zài wài​miàn hé rén gōu​da.

   He was cheating on his wife and carrying on with someone else.

   Source: Dong Chinese Dictionary

3. 那个男人背着妻子在外面找了一个情人。

   nà​gè nán​rén bèi zhe qī​zi zài wài​miàn zhǎo le yī gè qíng​rén.

   That man has a mistress behind his wife's back.

   Source: Dong Chinese Dictionary