Middle School - Grade 7
Lesson 2: Obligation & Necessity
-(아/어)야 되다 / 하다 (Must / Have to)
What Do You *Have* to Do?
This pattern is the most common way to say "must," "have to," or "should."
It's formed by combining the `아요/어요` conjugation (but you drop the `요`) and adding `~야 되다` or `~야 하다`.
`되다` (to become/be okay) and `하다` (to do) are almost perfectly interchangeable here. `하다` can sound slightly stronger or more formal, but both are used constantly.
Rule 1: "Must Do" (`-(아/어)야 되다`)
This follows the *exact* same rules as the `아요/어요` conjugation.
If stem's last vowel is `ㅏ` or `ㅗ`
Add -아야 되다
가다 가 + 야 되다 가야 돼요 (I have to go)
오다 와 + 야 되다 와야 돼요 (I have to come)
If stem's last vowel is *not* `ㅏ` or `ㅗ`
Add -어야 되다
먹다 먹 + 어야 되다 먹어야 돼요 (I have to eat)
If verb is `하다`
Becomes 해야 되다
공부하다 공부해야 돼요 (I have to study)
Rule 2: "Must Not Do" (`-(으)면 안 되다`)
This is for prohibition ("You must not," "You shouldn't"). It literally means "if you do (this), it is not okay."
If stem ends in a VOWEL or `ㄹ`
Add -면 안 되다
가다 가 + 면 안 되다 가면 안 돼요 (You must not go)
열다 열 + 면 안 되다 열면 안 돼요 (You must not open)
If stem ends in a CONSONANT (except `ㄹ`)
Add -으면 안 되다
먹다 먹 + 으면 안 되다 먹으면 안 돼요 (You must not eat)
Example Sentences
Must Do (`-야 되다`)
- 지금 가야 돼요. (I have to go now.)
- 숙제해야 돼요. (I have to do homework.)
- 뭐 먹어야 돼요? (What should I eat?)
Must Not Do (`-(으)면 안 되다`)
- 여기서 담배 피우면 안 돼요. (You must not smoke here.)
- 만지면 안 돼요. (You shouldn't touch it.)
- 늦으면 안 돼요! (You mustn't be late!)
Coming Up Next...
We've learned "must do" (`-야 되다`) and "must not do" (`-(으)면 안 되다`).
But what about "it's okay to..."? How do you ask for and give permission? That's our next lesson!