seal

1. Origins, structure, and basic meaning

• Structure: 封 conveys sealing or blocking; its on-reading is ふう.
• Basic usage: 封筒(ふうとう) means an envelope, while 封鎖(ふうさ) means a closure or blockade.

2. Common pitfalls and similar expressions

• An envelope for a letter and blocking passage
  • 封筒に入れて means putting something in an envelope, as in the letter example. 封筒 identifies the physical envelope.
  • 封鎖された means was closed or blocked off. The examples concern closing a bridge entrance after an accident or temporarily blocking roads by police.