# てはいけない: must not; may not > Learn how to use てはいけない, a JLPT N5 Japanese grammar point meaning must not; may not, with structure, nuance, examples, mistakes, and comparisons. JLPT level: N5 · Updated: 2026-05-17 · Canonical: https://hane-app.com/blog/n5-te-wa-ikenai/ **てはいけない** means **must not; may not**. It is a **JLPT N5** Japanese grammar pattern used to state that an action is not allowed. This grammar point appears often in beginner conversations, classroom Japanese, and JLPT-style questions. If you want to state that an action is not allowed, **てはいけない** is a useful pattern to learn because it helps you build natural basic sentences. ## What does てはいけない mean? Use **てはいけない** when you want to state that an action is not allowed. Natural translations include: - must not - may not - must not; may not The exact English translation changes with context. Focus on the role of the grammar point in the sentence first, then choose the English phrase that sounds natural. ## How to form てはいけない

Verb (て-form) + はいけない

Verb (て-form) + はいけません

Examples of the pattern: - 入はいってはいけない - 食たべてはいけない - 忘わすれてはいけない Pay attention to the word form before and after the pattern. Many beginner mistakes happen because the meaning is understood, but the grammar is attached to the wrong form. ## When is てはいけない used? Use **てはいけない** in situations like: - rules - warnings - prohibitions Tone and register: - firm; polite as てはいけません - Common in daily speech, textbook examples, and beginner JLPT questions ## てはいけない example sentences

ここで写真しゃしんを撮とってはいけません。

You must not take pictures here.

polite prohibition

この部屋へやに入はいってはいけない。

You must not enter this room.

plain rule

試験中しけんちゅうに話はなしてはいけません。

You must not talk during the test.

polite rule

約束やくそくを忘わすれてはいけません。

You must not forget the promise.

polite warning

夜よる遅おそく電話でんわしてはいけません。

You must not call late at night.

polite warning

Read the Japanese sentence first, then check the English translation. Try to notice what the grammar point contributes: question, contrast, reason, time limit, suggestion, negation, comparison, or obligation. ## Nuance of てはいけない The key nuance is **the action is prohibited or unacceptable**. This matters because beginner Japanese often uses small words and endings to show meaning that English expresses with word order or helper verbs. For **てはいけない**, the sentence can change a lot depending on placement and context. For example: - In conversation, it helps the listener understand the action is prohibited or unacceptable. - Compared with **ないでください**, it has a different job even when the English translation looks close.

📝

Remember: てはいけない states a rule or prohibition. If you want to ask someone politely, ないでください is usually the better choice.

## てはいけない vs ないでください Both **てはいけない** and **ないでください** can express related ideas, but they are different.

てはいけない

states a rule or prohibition

often stronger than a request

ここに入はいってはいけません。

You must not enter here.

ないでください

asks someone not to do something

sounds like a request

ここに入はいらないでください。

Please do not enter here.

If you are unsure which one to use, ask what the sentence is trying to do: ask a question, connect ideas, show a reason, mark time, make an invitation, compare two things, or express obligation. ## Common mistakes with てはいけない

❌

朝ご飯はんを食たべてはいけない。

✅

朝ご飯はんを食たべなくてはいけない。

Confusing てはいけない with なくてはいけない

❌

明日あしたは学校がっこうへ行いってはいけない。

✅

明日あしたは学校がっこうへ行いかなくてもいい。

Using it when you mean “do not have to”

❌

ここで写真しゃしんを撮とってはいけない。

✅

ここで写真しゃしんを撮とってはいけません。

Forgetting polite てはいけません in formal contexts

A good study habit is to write one short sentence and then change only the grammar point. This makes the difference between similar patterns easier to feel. ## Is てはいけない on the JLPT?

Yes. てはいけない is commonly taught as JLPT N5 grammar.

recognize it in reading
understand its nuance in context
use it in simple original sentences

For test preparation, do not only memorize the English gloss. Practice identifying the words around the grammar point, because JLPT questions often test structure and context together.

## Practice questions for てはいけない Try making your own sentences with these prompts:

1 Say you must not enter here. prohibition

2 Say you must not talk during the test. rule

3 Say you must not take pictures. warning

Keep the sentences short at first. Once the form feels natural, add time words, places, reasons, or contrast to make the sentence more realistic. ## Learning path for てはいけない Use **てはいけない** as part of your **JLPT N5** request, permission, prohibition, and obligation grammar toolkit. Check the social force of the sentence: request, invitation, permission, prohibition, advice, or necessity. Then practice changing the ending to make the sentence softer, stronger, positive, or negative.

Write one short sentence with てはいけない without looking at the pattern chart.

Compare it with ちゃいけない・じゃいけない to see how the tone changes.

Add ないでください or てもいいです to see how the basic meaning changes.

Write one example with a different subject or time word.

Write one example that contrasts it with a related pattern from the list below.

## Related grammar to review next - [ちゃいけない・じゃいけない](/blog/n5-cha-ikenai-ja-ikenai/) — contrasts request, permission, prohibition, advice, and obligation strength. - [ないでください](/blog/n5-naide-kudasai/) — contrasts request, permission, prohibition, advice, and obligation strength. - [てもいいです](/blog/n5-temo-ii-desu/) — contrasts request, permission, prohibition, advice, and obligation strength. - [なくてもいい](/blog/n5-naku-temo-ii/) — contrasts request, permission, prohibition, advice, and obligation strength. ## Learn てはいけない with Hane If you want to review **てはいけない** together with the related patterns above, Hane helps you practice Japanese in short, focused sessions. Browse more lessons here: - [All grammar lessons](/blog/) - [JLPT N5 grammar lessons](/blog/n5/)