んじゃない
Don't, Mustn't, Shouldn't have
Structure
Explanation
The grammar structure んじゃない is a casual way to tell someone not to do something, functioning as a prohibition or a strong negative request. It is typically translated as 'Don't (do something)' or 'You must not...'. This expression is generally used by someone in a position of authority speaking to a subordinate, like a parent to a child. While it can convey anger, it is also used for firm warnings.
Grammatically, んじゃない is formed by combining the nominalizing particle の (shortened to ん) with じゃない, the informal negative of です. It always follows the dictionary form of a verb.
- 夜遅くまでテレビを見るんじゃない。Don't watch TV so late at night.
- 危ないから、川の近くで遊ぶんじゃない！It's dangerous, so don't play near the river!
- 知らない人について行くんじゃないぞ！Don't go off with strangers!
While んじゃない is informal, a slightly more polite version, んじゃありません, is also used. This form allows the speaker to issue a firm prohibition without sounding overly aggressive, making it suitable for situations like a teacher correcting a student.
- 廊下を走るんじゃありません。You are not to run in the hallways.
- 食べ物で遊ぶんじゃありません。You shouldn't play with your food.
If translated more literally, Verb + んじゃない means 'it is not that (one) does the verb'. While this sounds unnatural in English, it carries a similar force to an English speaker saying 'You're not doing that,' to command someone to stop.
You will frequently see this pattern used with the contracted form of ている, which becomes てん just before じゃない.
- 授業中にスマホをいじってんじゃない！Don't be messing with your smartphone during class!
- ぼーっと立ってんじゃない！早く手伝って！Don't just stand there spacing out! Hurry up and help!
Caution
In its past tense form, んじゃなかった, this grammar expresses regret. It conveys the feeling that an action performed in the past was a mistake and 'should not have been done'.
- あんなにたくさんケーキを食べるんじゃなかった。I shouldn't have eaten so much cake.
- あんなひどいことを彼に言うんじゃなかった。I shouldn't have said such an awful thing to him.
Caution
Pay close attention to intonation when you hear んじゃない at the end of a sentence, as it can also be a question. A rising tone indicates that it is a shortened form of the speculative question んじゃないか.
- もしかして、道に迷ったんじゃない？Maybe they got lost?
The distinction between these two meanings of んじゃない is almost always clear from context and delivery. A question will end with a rising intonation, whereas a command will have a sharp, falling intonation.
Examples
人のせいにするんじゃない！
Don't blame other people!
母親：「食べ物で遊ぶんじゃない！」
Mother: 'Don't play with your food!'
簡単に諦めるんじゃない。
You shouldn't give up so easily.
あなた、また無駄遣いをするんじゃありません。
Hey, don't waste money again.
まだ病気ですよ。無理をするんじゃありません。
You're still sick. Don't push yourself too hard.
言い訳ばかりするんじゃない。
Don't just make excuses.
夜更かしするんじゃない。明日の朝、起きられないぞ。
Don't stay up late. You won't be able to wake up tomorrow morning!
あんなにたくさん食べるんじゃなかった…。
I shouldn't have eaten so much…
飲みすぎた…最後の一杯を飲むんじゃなかった。
I drank too much… I shouldn't have had that last drink.
夜遅くに電話してきて人を起こすんじゃない！
Don't call late at night and wake people up!
もうお金がない。あの株を買うんじゃなかった…。
I have no money left. I shouldn't have bought that stock…
先輩：「口答えするんじゃない！」
Senior: 'Don't talk back!'