Should not do with 〜てはいけない

Grammar: Prohibition » 〜てはいけない

2019年01月26日

2026年08月12日

〜てはいけない says that an action is forbidden or unacceptable: “must not” or “should not”.

Usage Notes

〜てはいけない tells the listener that doing the action is not acceptable, not that the speaker dislikes it.

In speech, ては contracts to ちゃ, producing forms like しちゃいけない.

Must not do with 〜てはだめだ
- Used to prohibit (rather than simply discourage) an action.
Must not do with 〜べからず
- An old-fashioned way to strongly forbid an action.

Cocoa prepares to teach her friends how to bake bread.

ココア:: 「みんな　パン作(つく)りをなめちゃいけないよ！」; “Everyone, don't underestimate bread making!”