Practice JLPTHow to tell them apart
な attaches directly to a verb and delivers a blunt, informal command not to do something, typically from a male speaker in casual speech. てはいけない uses the て-form plus てはいけない and expresses a rule or prohibition that applies regardless of who is speaking, often in formal contexts. Swapping them feels wrong because な is too rough for posted rules like 部屋に入ってはいけない, while てはいけない is too stiff for a direct personal order like 行くな！.
- な Use な when giving a blunt, informal command to someone not to do something, typically as a male speaker.
- はいけない Use てはいけない when stating a rule or prohibition that something must not be done, in formal or neutral contexts.
| Grammar point | Meaning | JLPT level |
|---|---|---|
| な na | Negative imperative (don't) | N5 |
| はいけない haikenai | Must not / prohibited | N4 |
な na
Negative imperative (don't)
Don't do ~ | A negative imperative marker used by a male speaker in very informal speech
-
あんな男とは結婚するな！
Don't marry that kind of man!
-
そんな所にもう行くな！
Don't go to such a place any more!
はいけない haikenai
Must not / prohibited
Cannot do something; must not do something; don’t do something; should not do something | A phrase which indicates prohibition.
-
この部屋に入ってはいけない・いけません。
You must not enter this room.
-
教室でものを食べてはいけません。
You must not eat (food) in the classroom.
な and はいけない are JLPT N5–N4 grammar points that Japanese learners often mix up. This page compares them side by side — meanings, usage and example sentences — so you can tell them apart.