2 sentences for 劲 (jìn — expression)

1. 瞧他那股认真劲儿。

   qiáo tā nà gǔ rèn​zhēn jìn r.

   Look at how serious he's being.

   Source: Dong Chinese Dictionary

2. 这孩子眼神里透着那么一股慧劲儿。

   zhè hái​zi yǎn​shén lǐ tòu zhe nà​me yī gǔ huì jìn r.

   There is a spark of intelligence in this child's eyes.

   Source: Dong Chinese Dictionary