两回事

兩回事
liǎnghuíshì
  1. two quite different things
  2. two unrelated matters

CEDICT

two entirely different matters

Wiktionary

两种迥然不同的事情。如：「率性而为与不负责任是两回事，你不要溷为一谈。」也作「两码事」。

重編國語辭典

Entry Composition

1 两 liǎng
  1. two
  2. both
  3. some
  4. a few
  5. tael, unit of weight equal to 50 grams (modern) or 1⁄16 of a catty 斤 jīn (old)
2 回事 huíshì (old) to report to one's master