JLPT N4 grammar

〜てはいけないmeaning and usage

Meaning

  1. May not A; must not A
  2. In order to avoid A; A would be bad, and so…

This point is also listed at N3.

How to form it

  • verb (te-form)はいけない
  • い-adjective (-く form)てはいけない
  • な-adjective (stem)/nounではいけない
  • 〜てはいけない → 〜ちゃいけない/〜ではいけない → 〜じゃいけない

How it is used

Prohibition, “must not”, typical of rules and warnings from parents or teachers; casually 「〜ちゃいけない」. It can also mean “it would be bad if…, so…”. The opposite of 「〜てもいい」.

Examples

  1. お父さんに逆らってはいけない。

    Don't go against your father.

  2. 図書館の中で食べ物を食べてはいけません。

    You must not eat food inside the library.

  3. 約束の時間に遅れてはいけないので、早く家を出た。

    I couldn't be late for the time we'd agreed, so I left home early.