modality N2 common politewritten
てはならない — must not ~
てはならない
Builds on てはいけない
Meaning
- must not ~ / one is not to ~ — a strong, formal prohibition, often a rule, principle, or moral imperative
Key sentence
この秘密を他人に漏らしてはならない。
You must not leak this secret to anyone.
Formation
| Attaches to | Form | Example |
|---|---|---|
| Verb て-form + はならない | Vて + はならない | 嘘をついてはならない |
When: Formal and weighty — laws, rules, contracts, moral statements, written notices. In everyday speech てはいけない / ちゃだめ are used instead.
Examples
戦争の悲劇を二度と繰り返してはならない。
The tragedy of war must never be repeated.
規則を破ってはならないことになっている。
It is established that the rules must not be broken.
When you can't use it
- Expresses an absolute prohibition grounded in a rule or principle; it sounds stiff and authoritative, unsuited to a casual one-on-one request.
Easily confused with
See てはならない in real sentences
Jengo shows てはならない the way you actually meet it: inside real Japanese sentences, so it sticks instead of staying an abstract rule.
Study it in JengoSources Compiled with reference to A Dictionary of Basic Japanese Grammar.