Lesson 19. Have to & must [verb-아/어야 되다(하다) & 반드시/꼭] & Negations

1. How to say, “I have to verb/adj” : Verb/Adjective-아/어야 되다, Verb/Adjective-아/어야 하다

Construction :
Verb -아/어(present stem)야 되다,
Verb-아/어(present stem)야 하다

Both are interchangeable and mean “have to.”

For example:

먹다 (to eat)  > 먹어야 되다 / 먹어야 하다 (to have to eat)

공부하다 (to study) > 공부해야 되다 / 공부해야 하다 (to have to study)

가다 (to go) > 가야 되다 / 가야 하다 (to have to go)

자다 (to sleep) > 자야 되다 / 자야 하다 (to have to sleep)

운동하다 (to exercise) > 운동해야 되다 / 운동해야 하다 (to have to exercise)

가르치다 (to teach) > 가르쳐야 되다 / 가르쳐야 하다 (to have to teach)

쓰다 (to write / use) > 써야 되다 / 써야 하다 (to have to write, use)

듣다 (to listen) > 들어*야 되다 / 들어야 하다 (to have to listen)
*듣다 follows an irregular conjugation rule 

행복하다 (to be happy) > 행복해야 되다 / 행복해야 하다 (to have to be happy)

건강하다 (to be healthy) > 건강해야 되다 / 건강해야 하다 (to have to be healthy)

똑똑하다 (to be smart) > 똑똑해야 되다 / 똑똑해야 하다 (to have to be smart)

noun 이다 (to be noun) >  (noun that ends in consonant) + 이어야 되다/ 이어야 하다, (noun that ends in vowel) + 여야 되다/여야 하다

Let’s look at some sentence examples.

When using it in a sentence, 되다 and 하다 are conjugated in its corresponding tenses :
Present – Verb-아/어야 돼요 (=해요) : have to verb
Past – Verb-아/어야 됐어요 (=했어요) : had to verb
Future – Verb-아/어야 될 거예요 (=할 거예요) : will have to verb

숙제를 내일까지 다 해야 돼요 (=해야 해요). – I have to finish the homework by tomorrow.

사람들을 친절하게 대해야 돼요 (=대해야 해요). – You have to treat people kindly. (대하다: to treat)

제 방이 지저분해서 청소해야 돼요 (=청소해야 해요). – My room is messy, so I have to clean it up.

오늘 단짝 친구의 생일이에요. 그래서 좋은 선물을 골라야 돼요 (=골라야 해요). – Today is my best friend’s birthday, so I have to pick out a good present. (고르다: to choose)

오래 살고 싶어요? 그러면 건강해야 돼요. (=건강해야 해요) Do you want to live long? Then you have to be healthy.

한국인 남자친구를 사귀고 싶어요? 그러면 한국어를 잘 해야 될 거예요 (=해야 할 거예요). – Do you want to date a Korean boyfriend? Then you will have to speak Korean well.

어제는 너무 피곤해서 일찍 자야 됐어요. (=자야 했어요.)  – I was too tired yesterday, so I had to sleep early.

2. How to say, “I/You must~” :

1) 반드시 / 꼭 + verb/adj-아/어야 되다, 하다

If you want to express a stronger obligation, almost like “must” in English, you can put the adverb 반드시 (or 꼭 = definitely) before V/A-아/어야 하다, 되다 construction. 

반드시 와야 해요! You definitely have to come! (=You must come!)

내일은 월요일이에요. 그래서 반드시 일찍 자야 돼요. Tomorrow is Monday, so I definitely have to (=must) sleep early!

마스크를 꼭 착용하세요. Make sure to wear a mask! (You must wear a mask!) 

한국에서는 술을 마시려면* 반드시 성인이어야 해요. To drink alcoholic beverage in Korea, you must be a legal adult. *Verb-(으)려면 means “If you want to/intend to verb,~”

2) V/A-아어야만 되다, 하다

Another way to say you MUST do something is by putting 만 after Verb-아/어야. This is literally emphasizing that you just have to do it, which can be translated as “must” in English.

오늘은 열 시 전에 자야만 해요. I must sleep before 10 pm today.

담배를 끊어야만 해요. You must quit smoking. 

3. Negation of “have to” and “must”

1) don’t have to, must not

When negating Verb-아/어야 되다/하다, you CANNOT say Verb-아/어야 안 되다/하다.

Verb-아/어야 되다,하다 cannot be negated this way.

There are separate constructions you can use to say “don’t have to” and “should/must not” each,

which are “안 V/A-아/어도 되다, V/A-지 않아도 되다 (don’t have to V/A)” and “Verb/Adj-(으)면 안되다(you should not V/A.)” We will learn this construction when we get to Beginner 3 Course. 

2) Don’t I/you/he/she/they have to~?

Verb-아/어야 되다, 하다 can be negated by using -지 않다 construction. So you can say, Verb-아/어야 되지 않다 or V/A-아/어야 하지 않다.

However, this does NOT mean “don’t have to” or “should not” in English. Instead, Verb-아/어야 되지 않다, 하지 않다 is used more often when asking questions like, “Don’t you/I have to~?”

e.g.

지수 씨 오늘 학교에 9시 까지 가야 되지 않아요? Jisoo, don’t you have to go to school by 9am today?

영화를 보려면 표를 예매해야 되지 않아요? Don’t I have to buy the ticket in advance to watch a movie? [표: ticket, 예매하다: to buy sth in advance]