Saying "You Must Not"
てはいけない is the direct opposite of てもいい. Where てもいい grants permission, this refuses it.
Verb [て form] + は + いけません
- ここで写真を撮ってはいけません。(You must not take photos here.)
It comes from いける (to be acceptable) in the negative — literally "doing that won't do."
The Permission Pair
| Pattern | Meaning |
|---|---|
| 入ってもいいです | You may enter |
| 入ってはいけません | You must not enter |
They are built the same way — て form plus a small ending — so learn them together.
ちゃ / じゃ in Speech
Nobody says てはいけない at full length in conversation. It contracts:
| Full | Contracted |
|---|---|
| 食べてはいけない | 食べちゃいけない |
| 飲んではいけない | 飲んじゃいけない |
て → ちゃ, で → じゃ. In very casual speech even いけない drops: 食べちゃだめ。
Who Says It to Whom
てはいけません carries authority — a rule-maker to a rule-follower. Signs, teachers, parents. Said sideways to a peer it sounds preachy.
Softer ways to stop someone:
- 触らないでください。(Please don't touch.) — ないでください
- ちょっと難しいですね。(That's a bit difficult…) — indirect refusal
だめ — The Everyday Version
In daily life だめ does most of this work:
- ここに入っちゃだめ。(You can't go in here.)
- だめです。(No / not allowed.)