ちゃだめ / じゃだめ

The grammar point ちゃだめ and じゃだめ is used to indicate that something is prohibited or not allowed. It is often employed in informal contexts.

When using this expression, you can replace the ちゃ with じゃ depending on the preceding word. ちゃ follows verbs ending with specific sounds (usually う-line verbs), while じゃ follows nouns or adjectives.

• ちゃだめ is more commonly used in casual conversations among friends.
• じゃだめ is commonly used for nouns and often sounds a bit more formal.

This expression emphasizes that something is not permitted. It's often used by parents to their children or in instructive situations.