扉

1. Origins, structure, and basic meaning

• Structure: 扉 is read as とびら and is a noun for a door or door panel, often one with a substantial physical presence.
• Basic usage: Distinguish 重い扉を押す for an object being pushed and 扉が閉まる for the door closing.

2. Common pitfalls and similar expressions

• Transitive action and intransitive change
  • を marks the door acted upon, while が marks it as the subject whose state changes.
• Door and panel
  • Both contexts refer to a physical door or panel that can be pushed or closed by wind; the word should not be broadened to the whole doorway opening.