을/를 vs 이/가 with 좋다 · 되다 · 필요하다 | Korean Grammar

A whole cluster of Korean predicates come out in English as ordinary transitive verbs — "I like coffee," "I need water," "I became a doctor," "I fear snakes" — and every English instinct says to make coffee, water, doctor, and snakes the object, marked with 을/를. That instinct is wrong, and it is one of the most persistent errors intermediate learners carry. In Korean these predicates are descriptive (what English grammar would call adjectives) or intransitive, and their complement is not an object at all: it is a subject, marked with 이/가. So "I like coffee" is 커피가 좋아요, literally "coffee is pleasing (to me)."

The governing distinction is simple to state and takes practice to feel: is the predicate a doing verb, which acts on an object (→ 을/를), or a being/feeling verb, which describes a state of affairs (→ 이/가)? Once you can sort a predicate into that box, the particle picks itself.

The governing test: doing or being?

Ask what the predicate really means in Korean, not what its English translation looks like.

좋다 does not mean "to like." It means "to be good / pleasing." So the pleasing thing is a subject.
필요하다 does not mean "to need." It means "to be necessary." So the necessary thing is a subject.
되다 does not mean "to make something." It means "to come to be / turn into." So the resulting role is a subject.

None of these has an agent acting on a patient. There is only a state, and the thing in that state is the grammatical subject. English hides this because it repackages every one of them as a transitive verb with a tidy object. Korean keeps the underlying logic visible right in the particle.

💡

Translate the Korean predicate literally before you choose the particle. If the honest gloss is "is good," "is necessary," "becomes," "is scary," "is sore" — there is no object, only a subject. Reach for 이/가, never 을/를.

좋다 · 싫다: the thing you like is the subject

좋다 (be good/likable) and its opposite 싫다 (be disagreeable) describe your feeling-state. The thing that pleases or displeases you is the subject.

저는 커피가 좋아요.

jeoneun keopiga joayo

I like coffee. (lit. 'as for me, coffee is pleasing')

저는 강아지가 좋아요.

jeoneun gang-ajiga joayo

I like dogs.

저는 매운 음식이 싫어요.

jeoneun maeun eumsigi sireoyo

I dislike spicy food.

Notice the double-subject shape: 저는 sets the topic ("as for me"), and 커피가 / 음식이 is the inner subject of the descriptive verb. That is the native frame for feelings, and putting 를 on the liked thing — ×커피를 좋아요 — breaks it. (The action verb 좋아하다 does take 를; that is the escape hatch below, and the whole story is on 좋아하다 vs 좋다.)

필요하다: what you need is the subject, not the object

필요하다 means "be necessary." The needed thing is what is necessary — so it is the subject.

지금 물이 필요해요.

jigeum muri piryohaeyo

I need water right now. (lit. 'water is necessary')

이 일에는 시간이 더 필요해요.

i ireneun sigani deo piryohaeyo

This job needs more time.

뭐가 제일 필요해요?

mwoga jeil piryohaeyo

What do you need most?

Here English speakers reach hardest for 을/를, because "need" feels like the most transitive verb in the world — you need something. But Korean is describing the thing as necessary, so ×물을 필요해요 is ungrammatical. If you want a truly transitive "need," Korean uses a different verb, 필요로 하다 (formal, written), which is rare in speech; in everyday Korean, 이/가 필요하다 is the only natural pattern.

되다: you don't "become a doctor," a doctor "comes to be"

되다 means "come to be / turn into." The resulting identity is a subject marked 이/가 — and 되다 flatly refuses 을/를.

언니는 의사가 됐어요.

eonnineun uisaga dwaesseoyo

My older sister became a doctor.

커서 요리사가 되고 싶어요.

keoseo yorisaga doego sipeoyo

I want to become a chef when I grow up.

벌써 저녁이 됐어요.

beolsseo jeonyeogi dwaesseoyo

It's already evening. (lit. 'evening has come to be')

×의사를 됐어요 is impossible — there is no version of 되다 that takes an object. The last example shows how far this reaches: even "it became evening" treats 저녁 as the subject that came into being. Compare the causative 만들다 / -게 하다 if you genuinely want "make someone into X"; plain 되다 is always intransitive.

무섭다 · 아프다: fear and pain are subjects too

Two more high-frequency descriptive verbs trip up the same instinct. 무섭다 means "be scary/frightening," so the frightening thing is the subject. 아프다 means "be sore/painful," so the aching body part is the subject.

저는 뱀이 무서워요.

jeoneun baemi museowoyo

I'm afraid of snakes. (lit. 'snakes are scary to me')

머리가 아파요.

meoriga apayo

I have a headache. (lit. 'my head is sore')

어제부터 목이 아파요.

eojebuteo mogi apayo

My throat has been sore since yesterday.

"I'm afraid of snakes" has 뱀 as subject, not object: ×뱀을 무서워요 is wrong. And you never "hurt your head" transitively for an ordinary ache — 머리가 아파요, with the head as subject. (When you actively injure a body part in an accident, that is a different, genuinely transitive verb, 다치다: 머리를 다쳤어요 "I hurt my head" — 를 is correct there because 다치다 is a doing verb.)

The escape hatch: switch to the -어하다 action verb

Korean gives you a way to recast a feeling-state as an action, and that verb takes 을/를. Adding -어하다 to a descriptive feeling verb turns it into a transitive action verb that recasts the experiencer as an active doer:

좋다 (be pleasing, 이/가) → 좋아하다 (to like, 을/를)
싫다 (be disagreeable, 이/가) → 싫어하다 (to dislike, 을/를)
무섭다 (be scary, 이/가) → 무서워하다 (to be afraid of / to dread, 을/를)

저는 커피를 좋아해요.

jeoneun keopireul joahaeyo

I like coffee. (standing preference — action verb 좋아하다)

동생은 뱀을 무서워해요.

dongsaeng-eun baemeul museowohaeyo

My younger sibling is afraid of snakes.

So both particles are available for "like" and "fear" — but only by switching verbs. With the bare descriptive verb (좋다, 무섭다), the complement is 이/가; with the -어하다 action verb (좋아하다, 무서워하다), it is 을/를. What you cannot do is mix them: 을/를 with 좋다 is the error. 필요하다 and 되다 have no -어하다 partner, so for them 이/가 is the only option, full stop.

💡

There is a bonus payoff to -어하다: it is also how you neutrally report someone else's feelings. A plain 좋다/무섭다 in the present tense defaults to the speaker's own inner state, so third-person feelings usually switch to 좋아하다/무서워하다. More on that constraint in 좋아하다 vs 좋다.

Common Mistakes

1. Object-marking the thing you like. 좋다 is descriptive; its complement is a subject.

❌ 저는 커피를 좋아요.

jeoneun keopireul joayo

Wrong — 좋다 takes a subject, not an object.

✅ 저는 커피가 좋아요.

jeoneun keopiga joayo

I like coffee. (or, with the action verb: 커피를 좋아해요)

2. Object-marking what you need. 필요하다 means "be necessary" — the needed thing is the subject.

❌ 물을 필요해요.

mureul piryohaeyo

Wrong — 필요하다 never takes 을/를.

✅ 물이 필요해요.

muri piryohaeyo

I need water.

3. Object-marking the role you become. 되다 is intransitive.

❌ 의사를 됐어요.

uisareul dwaesseoyo

Wrong — 되다 takes the resultant role as a subject.

✅ 의사가 됐어요.

uisaga dwaesseoyo

[I] became a doctor.

4. Object-marking an aching body part. For an ordinary ache, 아프다 is descriptive.

❌ 머리를 아파요.

meorireul apayo

Wrong — for a plain ache the body part is the subject.

✅ 머리가 아파요.

meoriga apayo

I have a headache.

5. Object-marking what scares you (with the bare verb). 무섭다 keeps 이/가; only 무서워하다 takes 을/를.

❌ 저는 뱀을 무서워요.

jeoneun baemeul museowoyo

Wrong — 무섭다 takes a subject; 을 needs the verb 무서워하다.

✅ 저는 뱀이 무서워요.

jeoneun baemi museowoyo

I'm afraid of snakes.

Key Takeaways

A predicate's English translation lies about its transitivity. Gloss the Korean verb literally: "is good," "is necessary," "becomes," "is scary," "is sore" all take a subject (이/가), not an object.
The core cluster: 좋다, 싫다, 필요하다, 되다, 무섭다, 아프다 — all 이/가.
되다 and 필요하다 are intransitive to the bone: 이/가 is the only option.
The -어하다 verbs (좋아하다, 싫어하다, 무서워하다) recast the feeling as an action and do take 을/를 — but you must switch verbs to earn the object particle.
See the subject particle 이/가 and the object particle 을/를 for the underlying case system, and 좋다 vs 좋아하다 as adjectives for the state-vs-action pair up close.

Now practice Korean

Reading grammar gets you part of the way. The exercises are where it sticks — free, no signup needed.

Start learning Korean→