てはいけないte wa ikenai“must not; may not”

てはいけない is how Japanese says an action is not allowed: “you must not,” “you may not,” “no ~ing.” It is a JLPT N5 pattern built from the て-form, and it is the phrase behind almost every rule you will hear in a Japanese classroom, museum, or train station: 写真を撮ってはいけません, “no photos.”

〜てはいけない literally means "if you do ~, it won't go well." Japanese forbids something by saying that doing it is no good.

What does てはいけない mean?

Break the pattern into pieces and the meaning makes sense:

• 〜て — doing the action
• は — as for (pronounced wa)
• いけない — is no good, won’t do

So 食べてはいけない is “as for eating, it’s no good,” which English turns into “you must not eat (it).” Natural translations include “must not,” “may not,” “can’t,” “not allowed to,” and on signs, “No ~.”

The pattern states a prohibition. It does not ask, suggest, or hint. When a teacher says 教室で食べてはいけません, there is no room for negotiation: eating in class is against the rules.

How to form てはいけない

Take the て-form of a verb and add はいけない (plain) or はいけません (polite).

• 入る → 入って → 入ってはいけない
• 食べる → 食べて → 食べてはいけない
• 話す → 話して → 話してはいけない
• する → して → してはいけない

Verbs whose て-form ends in で keep the で, so the pattern becomes ではいけない:

• 飲む → 飲んで → 飲んではいけない
• 泳ぐ → 泳いで → 泳いではいけない
• 遊ぶ → 遊んで → 遊んではいけない

The は is always written with the hiragana は but read “wa,” exactly like the topic particle. You will also hear the stronger てはだめ (casual, common with children) and, in speech, the contraction ちゃいけない / じゃいけない.

When is てはいけない used?

てはいけない fits any situation where someone states a rule:

• Public rules and signs: museums, pools, libraries, trains
• School and workplace rules: what students or staff may not do
• Parents to children: 道で遊んではいけません
• Answering a permission question: A asks 〜てもいいですか, B answers いいえ、〜てはいけません
• General moral statements: うそをついてはいけない, “you mustn’t lie”

The speaker is either someone with authority (teacher, parent, staff) or is describing a rule that exists regardless of who says it. That is why てはいけない sounds natural in a sign or a rule book, and too direct when you say it to your boss or a guest. You are not in a position to set rules for them.

Politeness level: use いけません with people you speak politely to (when you are explaining a rule, for example to a new classmate), and いけない with friends or family.

てはいけない example sentences

Nuance of てはいけない

てはいけない is firm. It is not “please don’t”; it is “this is not permitted.” The strength comes from the fact that it describes the action as wrong in general, not as a personal favour you are asking for.

That makes it a natural pair with てもいい (“it’s OK to”). Japanese textbooks teach them together: 〜てもいいですか asks for permission, and 〜てはいけません refuses it. In real conversation, though, a flat いいえ、吸ってはいけません can sound stiff. Japanese speakers often soften the refusal with すみません、ここはちょっと… or explain the rule instead: ここは禁煙なんです, “this is a no-smoking area.”

Also note what the pattern does not mean. てはいけない never means “don’t have to.” If something is simply unnecessary, you need なくてもいい instead.

💡 Double negative alert: add ない before て and the meaning flips. 食べてはいけない = "you must not eat." 食べなくてはいけない = "you must eat." One small なく changes a prohibition into an obligation.

てはいけない vs ないでください

Both stop someone from doing something, but they come from different places.

A museum sign might use てはいけません; a guard walking up to you would more likely say 撮らないでください. If you need someone to stop, ないでください is usually the safer choice. Use てはいけない when you are explaining what the rule is.

Common mistakes with てはいけない

Is てはいけない on the JLPT?

A common reading question shows a notice with several rules and asks what you are not allowed to do. Look for every verb ending in てはいけません or ないでください and check which one matches the answer.

Practice questions for てはいけない

Learning path for てはいけない

Related grammar to review next

• ないでください — the polite request version, better when you are asking a person rather than stating a rule.
• てもいいです — the permission question that てはいけません most often answers.
• ちゃいけない・じゃいけない — the same prohibition, contracted for casual speech.
• なくてはいけない — adds ない and turns “must not” into “must.”
• なくてもいい — “don’t have to,” which learners often confuse with “must not.”

Learn てはいけない with Hane

Hane has you practice てはいけない alongside てもいい and なくてはいけない, so you stop mixing up “must,” “must not,” and “may.” Try it in Hane.