Translation guide
Expresses prohibition or strong obligation not to do something. Japanese uses several negative obligation patterns, with the most common being 〜てはいけない and its contracted forms. The choice depends on formality, directness, and context.
ここでタバコを吸ってはいけません。
You must not smoke here.
遅れてはいけない。
You must not be late.
Express that someone is not allowed to do something or must avoid doing something.
Standard polite negative obligation. Used in rules, instructions, and general prohibitions. The 〜て form of the verb is followed by はいけない.
ここでタバコを吸ってはいけません。
You must not smoke here.
遅れてはいけない。
You must not be late.
More formal and written than 〜てはいけない. Often used in official rules, laws, and serious prohibitions.
この書類をなくしてはならない。
You must not lose this document.
秘密を漏らしてはならない。
You must not leak secrets.
Casual prohibition. だめ means 'no good' or 'not allowed'. Often used in everyday speech among friends or family.
そんなこと言ってはだめだよ。
You must not say things like that.
ここで遊んではだめ。
You must not play here.
Contracted casual form of 〜てはいけない. 〜ちゃ is used after verbs ending in 〜て, 〜で becomes 〜じゃ. Very common in informal speech.
Archaic or highly formal prohibition, often seen on signs or in old texts. Equivalent to 'thou shalt not'.
立ち入るべからず。
Do not enter. (You must not enter.)
Emphasize that there is no choice but to avoid doing something.
Literally 'must not do', but used to express 'must avoid doing'. The verb before なければならない is in negative form. This is a double negative construction.
失敗しなければならない。
You must not fail. (lit. You must not fail.)
遅刻しなければならない。
You must not be late.
Casual equivalent of 〜なければならない with negative verb. Expresses 'must not' in a less formal way.
忘れないといけない。
You must not forget.
Both mean 'must not', but 〜てはならない is more formal and often used in written rules or serious contexts. 〜てはいけない is suitable for everyday speech and general prohibitions.
English 'must not' is not directly translated as a single word. Using 〜なければならない with a positive verb means 'must do', not 'must not'. Ensure the verb before the pattern is in negative form for prohibition.