Grammar
-아/어야 하다
Meaning
Intermediate-a/eoya hada
Expresses obligation or necessity, similar to 'must' or 'have to' in English. It states that an action or state is required or unavoidable in order for something to be true or acceptable. Common in rules, laws, and general obligations.
Form
Attaches to a verb or adjective stem. If the stem's last vowel is ㅏ or ㅗ, add -아야 하다; otherwise add -어야 하다. 하다 verbs/adjectives become -여야 하다, which contracts to -해야 하다 in practice. Noun + 이다 becomes -이어야 하다 (with batchim) or -여야 하다 (without). 하다 can be replaced with 되다 (-아/어야 되다) in casual speech with the same meaning.
Examples
집주인은 보증금을 돌려주어야 합니다.
The landlord must return the deposit.
From: Jeonse and Wolse: Korea's Unique Deposit-Based Rental System
회사는 노동자에게 최저임금을 꼭 줘야 합니다.
Companies must pay workers at least the minimum wage.
모든 국민은 국민건강보험에 가입해야 합니다.
All citizens must join the national health insurance.
방은 항상 깨끗해야 합니다.
The room must always be clean.
Common mistakes & nuance
-아/어야 되다 is common in spoken Korean and means the same as -아/어야 하다; 하다 is slightly more formal/written.
Similar grammar
- -는 것이 좋다
-는 것이 좋다 means 'it's better to' — a soft recommendation. -아/어야 하다 states a real obligation or necessity, not just a suggestion.