Japanese grammar
What does ～てはいけない (extension) mean? Japanese grammar N4
～てはいけない (extension) means must not ~ (prohibited).
| Level (estimated, JLPT framework) | N4 |
|---|---|
| Structure | V て + はいけない V て + はならない (strict prohibition, regulations) V ちゃ／じゃ + いけない (shortened) |
| Romaji | ~ te wa ikenai |
| Meaning | must not ~ (prohibited) |
Forming it
| Verb | 吸う → 吸って → 吸ってはいけない |
|---|---|
| i-adjective | 高い → 高くて → 高くてはいけない |
| Spoken contraction | ～ては → ～ちゃ, ～では → ～じゃ (吸っちゃいけない, 飲んじゃだめ) |
| na-adjective / Noun | 不便 → 不便で → 不便ではいけない |
How to use it
Prohibiting something, stating that it's not allowed.
- This is a direct prohibition — strong and carrying authority. So it's only used TOP-DOWN: teacher → student, parent → child, sign/regulation → everyone. It's impossible for a subordinate to say this to a superior.
- Distinguishing the variants: いけない is used for specific everyday regulations, common in daily life; ならない is stricter, often used in laws, rules, formal writing; だめ is the most casual spoken version.
- The contracted forms ～ちゃいけない／～ちゃだめ sound very natural among friends and family. Note the contraction rule: ～って/～いて/～して → ちゃ; ～んで/～いで → じゃ (飲んで → 飲んじゃ).
- To prohibit something politely with a peer/guest, Japanese people usually avoid saying it directly: use ご遠慮ください (please refrain from...) — it sounds much softer.
Examples
ここで写真を撮ってはいけません。
You must not take photos here.
試験中に辞書を使ってはいけません。
You must not use a dictionary during the exam.
まだ寝ちゃだめだよ。宿題は？
You can't go to sleep yet. What about your homework?
Keep in mind
- Directly opposite ～てもいい (permission). N4 exams often pair these two together.
- On Japanese signs, instead of ～てはいけません, you often see ～禁止 (prohibited) or おタバコはご遠慮ください.
Common mistakes
-
Wrong部長、ここでたばこを吸ってはいけませんよ。
Department manager, you're not allowed to smoke here.
Correct部長、こちらは禁煙となっております。
A direct prohibition to a superior is impolite. With a boss/guest, state the REGULATION objectively rather than giving an order.
-
Wrong撮影禁止なので、ここで写真を撮らなくてはいけません。
Since this is a no-photography zone, photos are not allowed here.
Correct撮影禁止なので、ここで写真を撮ってはいけません。
～なくてはいけない means "must do," the opposite of prohibition. The stated reason (撮影禁止 - a no-photography zone) leads to the conclusion "must take photos" — a clear logical contradiction. For prohibition, use the affirmative て form + はいけない.
Exam tips
- Three easily confused patterns: ～てはいけない (prohibited) / ～なくてはいけない (must) / ～なくてもいい (no need to). Look carefully for ない and も.