函 hán correspondence
correspondence; letter
How it came to be
An arrow drawn point-down inside a quiver, the case closed round it. It was the case first; what came to be sent in a case was a letter, and the word went with it.
用法
- A formal letter/correspondence - 来函 (láihán) an incoming letter, 公函 (gōnghán) an official letter, 函授 (hánshòu) correspondence course.
- More formal than 信 (xìn); used for official and business correspondence.
- Separately, the math term 函数 (hánshù) function - an unrelated technical use.