-아/어야 하다/되다

How to use it

Expresses obligation or necessity: 'must, have to'. 되다 is more conversational; 하다 is neutral. Past: 가야 했어요 (had to).

Forming it

'Don't have to' is -지 않아도 되다, not ✗ -지 않아야 하다 (that means 'must not').

Examples

• 내일 시험이 있어서 공부해야 해요.

  I have a test tomorrow, so I have to study.

• 아침 일곱 시까지 공항에 가야 돼요.

  I have to get to the airport by 7 a.m.

Compared with similar patterns

-(으)면 안 되다 = must not; -지 않아도 되다 = don't have to; -아/어야겠다 = 'I'd better', the speaker's own decision.

Related patterns

• -(으)면 안 되다 must not, not allowed to
• -지 않아도 되다 don't have to, need not
• -아/어야겠다 I should, I'd better (the speaker's decision or resolve)