내일 시험이 있어요. 그래서 공부해야 돼요.
I have an exam tomorrow. So I must study.
여자 친구 생일이라서 선물을 사야 돼요.
It’s my girlfriend’s birthday, so I have to buy her a present.
먹기 전에 돈을 내야 해요.
You have to pay before you eat.
Grammar Focus:
-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 vowelㅏ 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.
A: 주말에 같이 영화 볼까요?
Shall we see a movie this weekend?
B: 미안해요. 어머니 생신이라서 고향에 가야 돼요.
Sorry, but it’s my mother’s birthday, and I have to visit home.
A: 여름에 제주도에 가려고 해요.
I’m planning to go to Jeju Island in the summer.
B 비행기표를 예악했어요? 사람이 많아서 미리 예약해야 돼요.
Did you reserve a plane ticket? A lot of people will be going there, so you have to reserve your ticket in advance.
A: 어제 왜 파티에 안 오셨어요?
Why didn’t you come to the party yesterday?
B: 일이 많아서 회사에서 일해야 됐어요.
I had a lot of things to do, so I had to stay at the office and work.
Notes:
-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.