～てはいけない (must not)

• Reading: てはいけない
• Romaji: te wa ikenai
• Formation: Verb て-form + はいけない / Verb て-form + はだめ / Verb て-form + はならない

Meaning

A phrase which indicates prohibition, expressing that an action is not allowed or must not be done.

てはいけない combines the て-form of a verb with はいけない to express prohibition. It is used by people in positions of authority such as parents, teachers, and superiors to forbid actions, or to state rules and regulations. The more formal variant is てはなりません, while casual contracted forms include ちゃいけない (from ては) and じゃいけない (from では). An even more casual form replaces いけない with だめ, as in ちゃだめ. This pattern expresses stronger prohibition than ないでください, which is simply a polite request not to do something.

Examples

1. ここで写真を撮ってはいけません。 You must not take photos here.
2. 授業中に携帯電話を使ってはいけません。 You must not use mobile phones during class.
3. 図書館で大きな声を出してはいけない。 You must not raise your voice in the library.

Usage Guide

Context: spoken, written, everyday

Tone: prohibitive

Do Say

• 試験中に辞書を使ってはいけません。
• ここでタバコを吸ってはいけません。
• 人の悪口を言ってはいけないよ。

Don't Say

• ここで走るはいけません。(Must use て-form: 走ってはいけません — dictionary form before はいけない is grammatically incorrect) → ここで走ってはいけません。
• 教室で食べてがいけません。(The particle after て-form is は, not が: 食べてはいけません) → 教室で食べてはいけません。

Origin & History

てはいけない literally means 'if one does X, it is not acceptable,' using the conditional は (from ては) plus いけない to express prohibition.

Cultural Context

Generation: All ages

Social background: Universal