-(으)면 안 되다
Must Not, Should Not
'-면 안 되다' expresses prohibition, meaning 'you must not' or 'it is not allowed.'
How It Works
'-면 안 되다' is a fundamental pattern for expressing that an action or state is forbidden or not permitted. It's a direct and clear way to state a rule or a strong negative consequence.
Conjugation:
The pattern follows the rules of -(으)면:
- If the verb/adjective stem ends in a vowel or 'ㄹ', add -면 안 되다.
- 가다 (to go) → 가면 안 되다
- 만들다 (to make) → 만들면 안 되다 - If the stem ends in a consonant (except 'ㄹ'), add -으면 안 되다.
- 먹다 (to eat) → 먹으면 안 되다
- 앉다 (to sit) → 앉으면 안 되다
Usage and Nuance:
This pattern does a different job from the command -지 마세요 ('please don't'). While '-지 마세요' tells a specific person not to do something, '-면 안 되다' states that doing it is against the rules or will lead to a bad outcome.
For example:
• 여기서 담배를 피우지 마세요. (Please don't smoke here.) - A request to the listener.
• 여기서 담배를 피우면 안 됩니다. (You must not smoke here.) - A statement of a rule.
Do not use it to say that you are unable to do something. 저는 매운 음식을 먹으면 안 돼요 means that a doctor or a rule forbids spicy food. If your body cannot handle it, use 못 or -ㄹ 수 없다, as in 저는 매운 음식을 못 먹어요.
The politeness level is adjusted by changing the ending of '되다':
- -면 안 돼 (Casual)
- -면 안 돼요 (Polite)
- -면 안 됩니다 (Formal)
This pattern is the direct opposite of -아/어도 되다, which grants permission ('you may...', 'it's okay to...').
Examples (5)
- 도서관에서는 큰 소리로 이야기하면 안 돼요.
You must not talk loudly in the library.
Word by Word: In the library if talk with a loud voice it is not okay.
- 수업에 늦으면 안 됩니다.
You must not be late for class.
Word by Word: To class if you are late it is not okay.
This example uses an adjective (늦다 - to be late) to state that a certain condition is not acceptable.
- 밤 10시 이후에는 컴퓨터 게임을 하면 안 돼.
You shouldn't play computer games after 10 PM.
Word by Word: Night 10 o'clock after computer games if you play it is not okay.
This is a casual form, often used by parents or between close friends.
- 운전 중에 휴대폰을 사용하면 안 됩니다.
You must not use your cell phone while driving.
Word by Word: During driving a cell phone if you use it is not okay.
- 다른 사람의 물건을 말없이 가져가면 안 돼요.
You shouldn't take other people's things without saying anything.
Word by Word: Other person's things without a word if you take it is not okay.
Common Mistakes
Leaving out 으 after a consonant stem.
Not Quite여기서 음식을 먹면 안 돼요.Better여기서 음식을 먹으면 안 돼요.A stem that ends in a consonant needs 으 before 면: 먹으면 안 돼요. Only stems that end in a vowel or ㄹ take plain 면, as in 가면 and 만들면.
Using -아/어도 안 돼요 to forbid something.
Different Meaning도서관에서 사진을 찍어도 안 돼요.Better도서관에서 사진을 찍으면 안 돼요.-아/어도 안 돼요 means 'even if you do it, it doesn't work', so it does not forbid anything. To say that you must not do something, use -(으)면 안 돼요.
Learn This First
To express conditional prohibition 'must not if', you need conditional forms and negation with 되다.
Related Patterns
- -아/어도 되다May, Be Allowed to
This is the direct opposite of '-면 안 되다'. It grants permission, meaning 'it is okay to...' or 'you may...'.
- -지 마세요Please Don't
Both express negative commands, but -지 마세요 is a request to a specific person ('Please don't...'), while '-면 안 되다' states a rule or prohibition ('You must not...').
- -아/어야 되다/하다Have to, Must
This expresses obligation ('must do', 'have to do'), which is the opposite concept of prohibition. One tells you what you must do, the other tells you what you must not do.
- -(으)ㄹ 수 있다/없다Can/cannot
This pattern expresses ability or possibility ('can'/'cannot'), whereas '-면 안 되다' expresses permission or prohibition. Learners often confuse inability with lack of permission.