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
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
- ここで写真を撮ってはいけません。 — You must not take pictures here.
- この部屋に入ってはいけない。 — You must not enter this room.
- 試験中に話してはいけません。 — You must not talk during the test.
- 約束を忘れてはいけません。 — You must not forget the promise.
- 夜遅く電話してはいけません。 — You must not call late at night.
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.
てはいけない:
- states a rule or prohibition
- often stronger than a request
ないでください:
- asks someone not to do something
- sounds like a request
Quick contrast examples:
- ここに入ってはいけません。— You must not enter here.
- ここに入らないでください。— 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
Watch out for these mistakes:
- Confusing てはいけない with なくてはいけない
- Using it when you mean “do not have to”
- 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.
That means learners should be able to:
- 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:
- Say you must not enter here.
- Say you must not talk during the test.
- Say you must not take pictures.
Keep the sentences short at first. Once the form feels natural, add time words, places, reasons, or contrast to make the sentence more realistic.
Learn てはいけない with Kanjiru
If you want to review てはいけない together with kanji, vocabulary, and other JLPT N5 patterns, Kanjiru helps you practice Japanese in short, focused sessions.
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