idiosyncrasy

One of his idiosyncrasies is that he always wears mismatched socks.

(Chinese) 他的一个癖好就是总是穿着颜色不匹配的袜子。

Every language has its own idiosyncrasies that make it difficult for foreigners to master.

(Chinese) 每种语言都有其独特的习惯，这使得外国人很难掌握。