The structure ～てはならない expresses a strong prohibition or moral imperative, meaning "must not" or "should not." It conveys that something is forbidden, unacceptable, or morally wrong, and carries a formal, often literary or authoritative tone. It is commonly found in written language, rules, laws, proverbs, and speeches.
。
You must not discriminate against people.
。
We must not forget this fact.
Comparison with ～てはいけない
Both ～てはならない and 〜～ては express prohibition ("must not"), but they differ in tone and usage:
- ～てはいけない is more conversational and is used in everyday situations, such as a parent telling a child not to do something or a teacher giving classroom instructions.
- ～てはならない is more formal, literary, and authoritative. It often expresses universal principles, moral obligations, or societal rules rather than personal or situational prohibitions.
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You must not use a dictionary during the exam. (practical rule)
。
One must not hide the truth. (moral principle)
Usage notes
～てはならない is rarely used in casual spoken conversation. It sounds solemn and carries weight, making it suitable for:
- Laws and regulations:
。
You must not enter without permission.
- Moral or ethical statements:
。
You must not bully the weak.
- Warnings or admonitions:
おなじ同じ。
We must not repeat the same mistake.
The contracted form ～ちゃならない (from ～てはならない) exists but is uncommon. The polite form ～てはなりません is used in formal spoken contexts.
Lingaku