[Easy Korean] Unit 17 -아/어야 해요 : must, have to, should

1. ‘-아/어야 하다’

‘-아/어야 해요’ expresses necessity. ‘-아/어야 해요’ is used with adjectives, verbs and ‘-이다/아니다’, ‘있다/없다’. If the last vowel of the stem is ‘아’ or ‘오’, ‘-아야 해요’ is added. If the last vowel of the stem is a vowel other than ‘아’ or ‘오’, ‘-어야 해요’ is added. If the same ends with ‘-하다’, then ‘-하다’ becomes ‘-해야 해요’.



오늘은 숙제가 많아요. 집에 가야 해요.
I have a lot of homework today. I should go home.

감기에 걸렸어요. 약을 먹어야 해요.
 I have a cold. I have to take medicine.

내일은 친구 생일이에요. 오늘 선물을 사야 해요.
Tomorrow is my friend’s birthday. I have to buy a present today.

내일 시험이 있어요. 오늘 밤에 공부해야 해요.
 I have exam tomorrow. I have to study tonight.

2. ‘-아/어야 되다’

‘아/어야 돼요’ and ‘아/어야 해요’ are the same in meaning, but  ‘-아/어야 돼요’ is slightly weaker than ‘-아/어야 해요’ . ‘-아/어야 돼요’ is used more often in colloquial situations.


점심을 먹어야 돼요.
I have to eat lunch.

오늘 공부해야 돼요.
I have to study today.

3. ‘-지 않아도 되다’

* -지 않아도 돼요 : (do) not have to, not necessary to do


내일은 휴일이에요. 회사에 가지 않아도 돼요.
Tomorrow is holiday. I don’t have to go to work.

무료 셔틀 버스예요. 티켓을 사지 않아도 돼요.
It is free shuttle bus. You don’t have to buy a ticket.