Grammar
N5 verb-grammar

Prohibition 〜てはいけません

Meaning

"You must not ~ / it's forbidden". Strong prohibition. Casual: 〜ちゃだめ / 〜てはいけない.

Formation

Notes

Direct counterpart of 〜てもいいです (permission). 〜てはだめです is a softer colloquial form. Signs often use dictionary form 〜な (立ち入り禁止, 飲むな).

Examples

You must not smoke here.

Breakdown
here at cigarette (object) must not smoke

You must not take photos.

Breakdown
photo (object) must not take

You must not use a phone in class.

Breakdown
classroom in mobile phone (object) must not use

You must not park here.

Breakdown
here at must not park

You must not make noise late at night.

Breakdown
night late at must not make noise

You must not run.

Breakdown
must not run

⚠️ Often confused with

Permission 〜てもいいです

"You may ~ / it's okay to ~". As a question (〜てもいいですか) = "May I ~?" As a statement...