"You must not enter this room." "You must not take photos."
To express Prohibition (rules or manners), we use "~te wa ikemasen". This is the opposite of "~temo ii desu ka".
1. Basic Structure
(You must not [Verb])
2. Restating Rules and Manners
Use this for public rules or things that are forbidden.
ここで写真を撮ってはいけません。
ここで しゃしんを とっては いけません
You must not take photos here.
教室で走ってはいけません。
きょうしつで はしっては いけません
You must not run in the classroom.
3. Casual Prohibition
Among friends and family, shortened forms or "~cha dame" / "~ja dame" are often used.
入っちゃだめ！
はいっちゃ だめ！
Don't enter! (Casual)
まだ食べちゃだめだよ。
まだ たべちゃ だめ だよ。
You can't eat it yet. / Don't eat it yet.
4. Summary
- Polite Prohibition → ~te wa ikemasen
- Plain Form → ~te wa ikenai
- Casual (Spoken) → ~cha dame / ~ja dame
⚡ Practice Quiz
Check your understanding!