封

封

"封" means "to seal," "to enclose," or "a measure word for letters."

'封' is a measure word used here to quantify '信' (letters).

我刚收到一封信。

I just received a letter.

Here, '封' functions as a descriptor for the notice, specifying its form or style.

他在门上贴了一封告示。

He posted a notice on the door.

'封' is used here as a verb meaning 'to seal' or 'to block off'.

这个房间被封起来了，不能进入。

This room has been sealed off and cannot be entered.