Last Updated：2025/11/19

must not (negative auxiliary); used to indicate that something is forbidden or, in a tag question, that something is not necessary.

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mustn't

Source Word

mustn't

IPA(Pronunciation)

Japanese Meaning

〜してはいけない / 必要ない

You mustn't leave your bike unlocked in this neighborhood.

この地域では自転車を無施錠のまま放置してはいけません。

Sense（1）

You mustn't blame yourself for this tragedy.