-아/어야 되다/하다 expresses an obligation or necessity to do something or the necessity of a certain condition.

It corresponds to 'must' or 'have (to)' in English.

If the stem ends in the vowel ㅏ or ㅗ, then -아야 되다/하다 is used, and for all other vowel endings, -어야 되다/하다 is used.

As for verbs ending in 하다, the form changes to 해야 되다/하다.

The past tense form is -아/어야 됐어요/했어요.

Details

-아/어야 되다/하다 has two negative forms, one meaning it is not necessary to do something, -지 않아도 되다 and the other expressing the prohibition of some behavior, -(으)면 안 되다.

1. -지 않아도 되다 (don't need to, don't have to)

A: 내일 회사에 가요?

Do you go to the office tomorrow?

B: 아니요. 내일은 휴가라서 회사에 가지 않아도 돼요.

No, tomorrow is a holiday, so I don't have to go to work.

A: 공원까지 버스로 가요?

(Do you) take the bus to the park?

B: 가까워요. 그래서 버스를 타지 않아도 돼요. 걸어가도 돼요.

(The park) is nearby. So I don't need to take the bus. I can walk.

2. -(으)면 안 되다. (shouldn't, be not allowed to)

박문관에서는 사진을 찍으면 안 돼요.

You're not allowed to take photographs inside the museum.

실내에서 담배를 피우면 안 돼요.

You should not smoke indoors.

Kimchi Reader

Express an obligation or necessity to do something.

Details

Negative forms

아/어야 되다/하다 has 2 negative forms: 1. 지 않아도 되다 = not necessary to do something. 2. (으)면 안 되다 = prohibition of some behavior.

A/V-아/어야 되다/하다

Kimchi Reader

Negative forms