Mastering the Korean grammar “-아/어야 되다/하다” is essential for expressing necessity and obligation. This grammar structure is widely used in daily conversations to say something must be done or is required. Whether you’re a beginner or intermediate learner, understanding how to use “-아/어야 되다/하다” will help you sound more natural in Korean. In this guide, we’ll explain its meaning, structure, and provide practical examples for effective usage.
Contents
1. Definition
“-아/어야 되다/하다” is used to express necessity, obligation, or something that must happen. It is equivalent to the English phrase “must” or “have to.” For example:
- “I have to study” → “공부해야 되다” (I must study.)
- “You must go” → “가야 되다” (You must go.)
2. Form (Structure)
-아/어야 되다/하다 is made up of:
- Verb/Adjective stem + 아야/어야 + 되다/하다.
- If the verb stem ends in a vowel similar to “ㅏ” or “ㅗ,” you use “아야.”
- If the verb stem ends in a different vowel, use “어야.”
| Verb Ending | Structure Used | Example |
| ㅏ, ㅗ | +아야 해야 되다/하다 | 가야 되다 / 가야 하다 (must go) |
| Other vowels | +어야 해야 되다/하다 | 먹어야 되다 / 먹어야 하다 (must eat) |
3. Meaning & Usage
- Expressing Obligation or Necessity
- This structure is commonly used when talking about rules, responsibilities, or necessary actions.
- Examples:
- 매일 숙제를 해야 돼요. (I must do my homework every day.)
- 약을 꼭 먹어야 해요. (You must take the medicine.)
- 버스를 타려면 마스크를 써야 돼요. (You must wear a mask to take the bus.)
- 이 일을 마감일까지 끝내야 해요. (I have to finish this work by the deadline.)
- 건강을 위해 충분히 자야 해요. (You must sleep enough for your health.)
- This structure is commonly used when talking about rules, responsibilities, or necessary actions.
- Interchangeability of ‘되다’ and ‘하다’
- Both “-아/어야 되다” and “-아/어야 하다” are grammatically correct and mean the same thing.
- Examples:
- 숙제를 해야 돼요 / 숙제를 해야 해요. (I have to do my homework.)
- 한국어 시험을 준비해야 돼요 / 한국어 시험을 준비해야 해요. (I must prepare for the Korean test.)
- 계약서를 확인해야 돼요 / 계약서를 확인해야 해요. (You must check the contract.)
- 주말에는 집 청소를 해야 돼요 / 주말에는 집 청소를 해야 해요. (I have to clean the house on weekends.)
- 비밀번호를 변경해야 돼요 / 비밀번호를 변경해야 해요. (You must change your password.)
- Both “-아/어야 되다” and “-아/어야 하다” are grammatically correct and mean the same thing.
- Used with Verbs and Adjectives
- It is mainly used with verbs, but some adjectives can also use this structure to indicate a necessary state.
- Examples:
- 여권이 유효해야 돼요. (Your passport must be valid.)
- 건강 검진 결과가 정상이어야 해요. (Your health checkup result must be normal.)
- 서류가 정확해야 해요. (The documents must be accurate.)
- 날씨가 좋아야 돼요. (The weather must be good.)
- 이 책이 쉬워야 돼요. (This book must be easy.)
- It is mainly used with verbs, but some adjectives can also use this structure to indicate a necessary state.
- Cannot be Used in Imperative or Propositional Sentences
- Instead of using “-아/어야 되다/하다” in commands, Korean uses expressions like “(으)세요” or “(으)면 좋겠어요” to make polite requests or suggestions.
- Examples:
- 빨리 가야 돼요! → ✅ 빨리 가세요! (You must go quickly! → Please go quickly!)
- 이 약을 먹어야 해요! → ✅ 이 약을 드세요! (You must take this medicine! → Please take this medicine!)
- 도서관에서 조용해야 돼요! → ✅ 도서관에서 조용히 해 주세요! (You must be quiet in the library! → Please be quiet in the library!)
- 회의에서 적극적으로 참여해야 해요! → ✅ 회의에서 적극적으로 참여해 주세요! (You must participate actively in the meeting! → Please participate actively in the meeting!)
- 늦게 오면 안 돼요! → ✅ 늦게 오지 마세요! (You must not come late! → Please don’t come late!)
- Instead of using “-아/어야 되다/하다” in commands, Korean uses expressions like “(으)세요” or “(으)면 좋겠어요” to make polite requests or suggestions.
4. Key Points to Remember
- “-아/어야 되다” expresses necessity or obligation due to external circumstances.
- “-아/어야 하다” emphasizes internal or moral obligations.
- The verb stem must be followed by “아/어야” depending on the vowel.
- “되다” and “하다” can be used interchangeably after “아/어야.”
5. Practice Exercises
- 나는 내일 중요한 시험을 ____________________. (I must prepare for the important exam tomorrow.)
- 우리는 매일 규칙적으로 ____________________ . (We should exercise regularly every day.)
- 저는 내일 학교에 ____________________ . (I must go to school tomorrow.)
- 그녀는 내일 중요한 발표를 잘 ____________________ . (She should do well on the important presentation tomorrow.)
- 우리는 서로를 ____________________ . (We should respect each other.)
- 나는 내일 병원에 ____________________ . (I must go to the hospital tomorrow.)
- 우리는 지속 가능한 삶을 위해 ____________________ . (We should strive for a sustainable life.)
- 우리는 진실을 ____________________ . (We should tell the truth.)
- 저는 내일 도서관에 ____________________ . (I must go to the library tomorrow.)
- 우리는 사회적 책임을 ____________________ . (We should fulfill our social responsibilities.)
6. Answers
- 준비해야 돼요/해요
- 운동해야 돼요/해요
- 가야 돼요/해요
- 해야 돼요/해요
- 존중돼요/해요
- 가야 돼요/해요
- 노력 돼요/해요
- 말해야 돼요/해요
- 가야 돼요/해요
- 다해야 돼요/해요
7. Common Mistakes and Tips
⚠️ Using ‘-아/어야 되다/하다’ in Commands
When giving instructions or making requests, it’s more polite to use expressions like “(으)세요” instead of “-아/어야 되다/하다.”
Direct Expression
- 빨리 가야 돼요! (You must go quickly!)
- 이 약을 먹어야 해요! (You have to take this medicine!)
- 도서관에서 조용해야 돼요! (You must be quiet in the library!)
Polite Alternative ✅
- 빨리 가세요! (Please go quickly!)
- 이 약을 드세요! (Please take this medicine!)
- 도서관에서 조용히 해 주세요! (Please be quiet in the library!)
💡 Tip: When giving instructions or making polite requests, use (으)세요 instead for a more polite tone.
⚠️ Mistake 2: Using ‘되다’ and ‘하다’ Incorrectly
Both -아/어야 되다 and -아/어야 하다 are correct and interchangeable in most cases. However, 되다 is more commonly used in spoken language, while 하다 is slightly more formal.
- 숙제를 해야 해요. / 숙제를 해야 돼요. (Both are correct.)
- 시험을 준비해야 해요. / 시험을 준비해야 돼요. (Both are correct.)
💡 Tip: If you’re unsure which one to use, just remember that both 되다 and 하다 are acceptable, but 하다 sounds a bit more formal.
⚠️ Mistake 3: Using This Structure with the Wrong Adjectives
This structure is mostly used with verbs, but some adjectives can also use it when expressing a necessary condition. However, not all adjectives work with this form.
Less Common or Unnatural Examples
- 기분이 좋아야 돼요. (You must feel good.) → This sounds unnatural.
- 눈이 커야 해요. (Your eyes must be big.) → This is not a natural use of necessity.
Correct ✅
- 여권이 유효해야 돼요. (Your passport must be valid.)
- 건강 검진 결과가 정상이어야 해요. (Your health checkup result must be normal.)
- 서류가 정확해야 해요. (The documents must be accurate.)
💡 Tip: Use this structure with adjectives only when expressing a necessary condition (e.g., something that “must” be a certain way).
⚠️ Mistake 4: Using ‘-아/어야 되다/하다’ in Past or Future Tense Incorrectly
This structure itself is in the present tense, so to talk about the past or future, the main verb (되다/하다) should be conjugated accordingly.
Less Accurate Expressions
- 어제 일찍 자야 됐어요. (I must have slept early yesterday.)
- 내일까지 보고서를 끝내야 될 거예요. (I must finish the report by tomorrow.)
Correct ✅
- 어제 일찍 자야 했어요. (I had to sleep early yesterday.)
- 내일까지 보고서를 끝내야 할 거예요. (I will have to finish the report by tomorrow.)
💡 Tip: When talking about the past, use -아/어야 했다. When talking about the future, use A-아/어야 할 것이다.
The grammar -아/어야 되다/하다 is essential for expressing obligation, necessity, or required conditions in Korean. It can be used with both verbs and certain adjectives, but should be avoided in commands or suggestions. While 되다 and 하다 are interchangeable, 되다 is more common in spoken language, and 하다 sounds slightly more formal. To express past or future necessity, remember to conjugate 되다/하다 accordingly. Mastering this structure will help learners express duties and requirements clearly in Korean.