てはいけない・
てはいけない says something is not allowed: "must not". It is how a rule is stated. In conversation it often shortens to ちゃいけない or ちゃだめ.
a rule
You must not speak loudly in the library.
in conversation
You can't cross the road when the light is red.
How to form it
Verb in the て-form + はいけない
入って → 入ってはいけない, 飲んで → 飲んではいけない. Polite いけません. The は is said "wa".
In conversation
ては → ちゃ では → じゃ
入っちゃいけない, 飲んじゃいけない. だめ can stand in for いけない: 入っちゃだめ, 飲んじゃだめ.
Stating a rule: てはいけません
A teacher says it to a class, a doctor to a patient, a guide to a group. It is also how you talk about a rule you are under yourself.
Bicycles must not be parked here.
Don't play here; it's dangerous.
When I was a child, I wasn't allowed to watch TV at night.
いけなかった: that was the rule then.
In conversation: ちゃいけない, ちゃだめ
だめ is the everyday word for "no good". It is what parents say to children and friends say to each other.
Children can't go to the river by themselves.
You must not take all the medicine at once.
Don't eat that yet.
I can't be late tomorrow.
About yourself, it is a reminder.
Telling, not asking
It lays down a rule. Coming from a colleague or a stranger, that sounds like a telling-off. To ask someone not to, people say ないでください.
You must not take photos here.
The rule, from a guard or a guide.
Please do not take photos here.
A request. Polite from anyone.
The same goes for a no to てもいいですか.
May I eat my lunch here?
No, you must not eat here.
B is a teacher or a guard. A colleague would trail off: すみません、ここはちょっと…….
The short no is だめです, or だめ to a child or a friend. It is as flat as てはいけません, so staff and colleagues soften it: すみません、ここはだめなんです.
Can I eat this?
No, no. It's still hot.
May I take pictures here?
Sorry, I'm afraid not here.
May, must not, don't have to
Three forms that go together. Word for word, they say:
You may use a dictionary.
"Even if you use one, it's fine."
You must not use a dictionary.
"If you use one, it's no good."
You don't have to use a dictionary.
"Even if you don't use one, it's fine."
も comes before いい, and は before いけない.
Must not, or must?
With a ない in front, the meaning turns around: now not doing it is what is no good.
You must not go home.
帰ってはいけない: going home is no good.
You have to go home.
帰らなくてはいけない: not going home is no good.
Close neighbours
なくてもいいN5
Takes a duty away. As a question, it checks whether you have to.
Is it okay not to copy this document?
てはならないN2
The written version, for laws and regulations.
No one may enter the storage room without permission.
ちゃう・じゃうN4
The same ちゃ sound, but it says something got done, often by accident. What follows tells you which.
I accidentally left my key at home.
Check yourself
1Which one fits?
ここで
Choose an answer to see why.
2What does this mean?
明日は
Choose an answer to see why.
3Who would say this?
教室で
Choose an answer to see why.
More sentences
You may not use a dictionary during the exam.
You must not enter this room.
You can't take pictures here.
You can't touch the wound yet.
You can't make a racket on the train.
You must not run in the hallway.