-아/어야 하다 / -아/어야 되다
Expresses a requirement, necessity, or obligation — either external (a rule or circumstance) or internal (the speaker's moral sense).
Summary
Equivalent
Must / Have to / Need to
Also: -아/어야겠다 (I must... — expressing personal resolve rather than external obligation)
Example
I have to submit an assignment by tomorrow so I need to stay up all night tonight.
내일까지 과제를 제출해야 해서 오늘 밤새워야 해요.
Grammar rules
- '-아/어야 하다' and '-아/어야 되다' are interchangeable in most contexts.
- '-하다' is slightly more formal in writing; '-되다' is more common in speech.
Patterns
Verbs (Obligation)
Present/Future · Verb/Adj Stem + 아/어야 하다
Same meaning, slightly softer
Present/Future · Verb/Adj Stem + 아/어야 되다
Example sentences
I have to submit an assignment by tomorrow so I need to stay up all night tonight.
내일까지 과제를 제출해야 해서 오늘 밤새워야 해요.
You need to exercise regularly for your health.
건강을 위해서 규칙적으로 운동해야 돼요.
You must have a passport if you want to go abroad.
외국에 나가려면 여권이 있어야 해요.
Conversation
A: Can I cancel today's appointment?
오늘 약속 취소해도 돼요?
B: No, it's an important meeting so you absolutely must attend.
아니요, 중요한 회의라서 꼭 참석해야 해요.
Practice
Fill in the blank
Express obligation or necessity.
Flu shot.
Must return book.