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
Examples of the pattern:
- 入ってはいけない
- 食べてはいけない
- 忘れてはいけない
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
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.
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.
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
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:
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.
Related grammar to review next
- ちゃいけない・じゃいけない — contrasts request, permission, prohibition, advice, and obligation strength.
- ないでください — contrasts request, permission, prohibition, advice, and obligation strength.
- てもいいです — contrasts request, permission, prohibition, advice, and obligation strength.
- なくてもいい — 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:
FAQ about てはいけない
What does てはいけない mean in Japanese?
てはいけない means “must not; may not” in Japanese. It is an N5 grammar point, and this lesson explains its formation, nuance, example sentences, common mistakes, and similar grammar.
Is てはいけない on the JLPT?
てはいけない is taught as N5 Japanese grammar in Hane's grammar lesson archive. Review it with examples, usage notes, and related N5 patterns.
How should I practice てはいけない?
Read several example sentences, identify the form before and after てはいけない, then make your own short sentences and compare it with nearby grammar points.