This phrase means 'you must not' or 'you can't'. It tells someone not to do something.
Verb [じゃ-form] + だめPrimary
This phrase means 'you must not' or 'you can't'. It tells someone not to do something.
子供はビールを飲んじゃだめだよ。
Kids are not allowed to drink beer.
あんなに急いじゃだめだった。結局、忘れ物したし。
I shouldn't have rushed that much. I ended up forgetting something, after all.
危ないから道路で遊んじゃだめって、言ったでしょ！
I told you not to play in the road because it's dangerous, didn't I!
この川で泳いじゃだめ。サメが出るらしいよ。
You can't swim in this river. I hear there are sharks.
大事な試験の前日に、徹夜で漫画を読んじゃだめだぞ。
You must not stay up all night reading manga the day before an important exam!
This phrase is like a parent telling a child "No!" It is very direct. Use it only with family or close friends. Never use it with bosses or strangers.
This is like saying "no good" or "you can't." It is a shorter way to say "〜ではだめ." It is more casual than "〜てはいけません." You use "〜じゃだめ" when a word's "-te" form ends in "-de." You use "〜ちゃだめ" when it ends in "-te."
Don't use this when you want to be polite. For example, don't say "タバコを吸っちゃだめです" to your boss. This rule is for certain verbs. It is for verbs that end in "-んで" or "-いで" in their "-te" form. For example, "飲む" becomes "飲んで". Then it becomes "飲んじゃ". "急ぐ" becomes "急いで". Then it becomes "急いじゃ". If a verb's "-te" form ends in "-て", use "〜ちゃだめ" instead.
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