2 sentences for 私 (sī — secretly)

1. 他们决定私奔到远方。

   tā​men jué​dìng sī bēn dào yuǎn​fāng.

   They decided to elope to a distant place.

   Source: Dong Chinese Dictionary

2. 他竟敢私自拿走公司的重要文件，真是太胆大了。

   tā jìng gǎn sī zì ná​zǒu gōng​sī de zhòng​yào wén​jiàn, zhēn shì tài dǎn​dà le.

   He was so bold as to take important company documents without permission.

   Source: Dong Chinese Dictionary