modality N5 essential casualpolitewritten

てはいけない — must not ~

てはいけない

Builds on ては

Meaning

must not ~ / you may not ~ — states a prohibition

Key sentence

ここで写真しゃしんを撮とってはいけない。

You must not take photos here.

Formation

Attaches to	Form	Example
Verb (て-form)	V-て + はいけない	入はいる → 入はいってはいけない

When: States a rule or prohibition and can sound strongly authoritative — common from a person in authority (teacher, sign, parent).

Variants

てはならない — formal / written prohibition ちゃいけない / ちゃだめ — casual contraction of ては → ちゃ: 入はいっちゃだめ

Easily confused with

〜てもいいてはいけない forbids; 〜てもいい permits. They are direct opposites: 食たべてはいけない (you mustn't eat it) vs 食たべてもいい (you may eat it). 〜なければならないてはいけない forbids doing X; なければならない requires doing X. 'Must not' vs 'must' — don't confuse the prohibition with the obligation.

See てはいけない in real sentences

Jengo shows てはいけない the way you actually meet it: inside real Japanese sentences, so it sticks instead of staying an abstract rule.

Study it in Jengo

Sources Compiled with reference to A Dictionary of Advanced Japanese Grammar, A Dictionary of Basic Japanese Grammar, A Dictionary of Intermediate Japanese Grammar.

← Back to the grammar tree