Obligation -아/어야 하다/되다 in Korean

Overview

The obligation pattern -아/어야 하다 or -아/어야 되다 expresses "must" or "have to" in Korean at the CEFR A2 level. The stem takes -아/어야 (same vowel harmony), followed by 하다 or 되다. Both mean essentially the same thing, with 되다 being slightly more colloquial. The negative "don't have to" is -지 않아도 되다, and "must not" is -(으)면 안 되다.

How It Works

Expression	Pattern	Example
Must/have to	stem + 아/어야 하다/되다	가야 해요 (have to go)
Don't have to	stem + 지 않아도 되다	안 가도 돼요 (don't have to go)
Must not	stem + (으)면 안 되다	가면 안 돼요 (must not go)

Examples in Context

Korean	Romanization	English	Note
가야 해요.	ga-ya hae-yo	(I) have to go.	obligation
공부해야 돼요.	gong-bu-hae-ya dwae-yo	(I) have to study.	하다 verb
안 가도 돼요.	an ga-do dwae-yo	(You) don't have to go.	no obligation
여기서 담배 피우면 안 돼요.	yeo-gi-seo dam-bae pi-u-myeon an dwae-yo	Must not smoke here.	prohibition
내일까지 끝내야 해요.	nae-il-kka-ji kkeun-nae-ya hae-yo	Have to finish by tomorrow.	deadline
일찍 일어나야 돼요.	il-jjik i-reo-na-ya dwae-yo	Have to wake up early.	routine obligation
숙제를 해야 해요.	suk-je-reul hae-ya hae-yo	Have to do homework.	school
지금 가야 돼요.	ji-geum ga-ya dwae-yo	Have to go now.	urgency
예약해야 해요?	ye-ya-kae-ya hae-yo	Do (I) have to make a reservation?	question

Common Mistakes

Confusing -아/어야 하다 with -(으)면 되다

• Wrong: Using them interchangeably
• Right: -아/어야 하다 = must do; -(으)면 되다 = it's enough to do / just need to
• Why: 가야 해요 (must go) vs. 가면 돼요 (it's fine if you go / just go).

Wrong negation pattern

• Wrong: 안 가야 해요 (don't have to go?)
• Right: 안 가도 돼요 (don't have to go) or 가면 안 돼요 (must not go)
• Why: "Don't have to" and "must not" have completely different structures in Korean.

Incorrect vowel harmony

• Wrong: 먹아야 해요
• Right: 먹어야 해요
• Why: 먹 stem has ㅓ vowel, taking -어야, not -아야.

Usage Notes

하다 and 되다 are interchangeable in this pattern, but 되다 is more common in casual speech. In formal writing, 하다 is preferred. The question form 해야 해요? is very common for asking about requirements. In casual speech: 가야 해 / 가야 돼.

Practice Tips

• Practice obligations for different life roles: as a student (공부해야 해요), as a worker (일해야 해요), as a parent (요리해야 해요).
• Practice the prohibition pattern with public rules: 여기서 ...하면 안 돼요.
• Pair "have to" with "don't have to" for the same verb to contrast.

Related Concepts

• Prerequisite: Polite Ending -아/어요 — same vowel harmony base
• Next steps: Permission -아/어도 되다 — the permission pattern using 되다