2 sentences for 一回事 (yī​huí​shì — one thing)

1. 你老板是怎么一回事？

   nǐ lǎo​bǎn shì zěn​me yī​huí​shì?

   What's up with your boss?

   Source: OpenSubtitles

2. 理论是一回事，实践又是另一回事。

   lǐ​lùn shì yī​huí​shì, shí​jiàn yòu shì lìng yī​huí​shì.

   Theory is one thing, practice is another.

   Source: Dong Chinese Dictionary