ちゃいけない・
ちゃいけない and じゃいけない casually say that an action is not allowed. They are common spoken shortenings of the ordinary prohibition pattern.
Choosing between the two forms
First make the verb’s te-form. If it ends in て, use ちゃいけない; if it ends in で, use じゃいけない. Do not choose only from the verb-group label.
Everyday prohibitions
These forms often appear in warnings, advice, and rules stated during conversation.
Do not confuse these patterns
てはいけない is the full form of the same prohibition and is better suited to careful writing. By contrast, ちゃう・じゃう is a different shortening associated with completion or regret. A dictionary-form verb followed by な is a direct prohibitive command and normally sounds more abrupt.
More examples
子どもだけで川に行っちゃいけないよ。
Children mustn't go to the river by themselves.
Analyze電車の中で騒いじゃいけない。
You mustn't make a racket on the train.
Analyzeまだ傷に触っちゃいけないよ。
You mustn't touch the wound yet.
Analyzeここで遊んじゃいけません。
You mustn't play here.
Analyze大事な書類をなくしちゃいけない。
You mustn't lose the important documents.
Analyze赤信号で道を渡っちゃいけないよ。
You mustn't cross the road when the light is red.
Analyze