This means you must not do something. It tells you what is not allowed. You use it for rules or strong orders.
Verb [て-form] + は + いけないPrimary
Verb [ちゃ-form] + いけない
Verb [じゃ-form] + いけない
This means you must not do something. It tells you what is not allowed. You use it for rules or strong orders.
この部屋ではタバコを吸ってはいけない。
You must not smoke in this room.
あんなにたくさん食べてはいけなかった。お腹が痛い。
I shouldn't have eaten that much. My stomach hurts.
図書館では大声で話してはいけないので、静かにしましょう。
Since you are not allowed to speak loudly in the library, let's be quiet.
危険な場所だから、絶対に行ってはいけないというわけではないが、注意は必要だ。
It's a dangerous place, so it's not that you absolutely must not go, but you do need to be careful.
夜遅くまでゲームをしちゃいけないよ。明日学校でしょ？
You shouldn't play games until late at night. You have school tomorrow, right?
This grammar has a shorter, more casual form. It is like saying 'gonna' instead of 'going to'. You will hear it a lot when people talk to friends or family.
This is a direct rule. It means you must not do something. It is like '〜てはだめ' and '〜てはならない'. But '〜てはだめ' is more casual. A parent might say it to a child. '〜てはならない' is very formal. You see it in laws.
Use this when you want to say something is not allowed. It is like saying "You must not do this." You use it for rules. You also use it for things that are not safe. People in charge often use it. For example, a teacher might use it. It is a very direct way to speak.
Often confused with(1)
Contrasts with(1)
More formal alternatives(1)
Less formal alternatives(1)
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