In short

을/를 marks the direct object - the thing the action is done to - and it glues onto the noun with no space: 을 after a 받침, 를 after a vowel. The catch for English speakers is that Korean and English disagree about which verbs even take an object, so you have to learn the particle together with the verb.

The rule

Step 1 - Choose the shape from the 받침

Exactly the same mechanism as 이/가 and 은/는. Look at the last syllable of the noun, not at the word’s meaning:

• Noun ends in a consonant (받침) -> 을. 책 -> 책을 (chaegeul, a book), 밥 -> 밥을 (babeul, a meal).
• Noun ends in a vowel -> 를. 사과 -> 사과를 (sagwareul, an apple), 커피 -> 커피를 (keopireul, coffee).

ㄹ is a 받침 like any other, so it takes 을: 물 -> 물을 (mureul, water), 서울 -> 서울을 (Seoureul, Seoul). Writing *사과을 or *책를 is a spelling error, not a variant.

Step 2 - Where the object sits

Noun + 을/를 + Verb. The object comes before the verb, and the verb still closes the sentence:

• 저는 사과를 먹어요. (Jeoneun sagwareul meogeoyo.) - I eat an apple.

Because the particle carries the role, the object can be moved for emphasis without becoming the subject - but at A1 keep the neutral order.

Step 3 - Verbs whose case frame will surprise you

This is the real work of this lesson. English marks these roles with a preposition; Korean simply calls them the object and puts 을/를 on them. Learn each verb with its particle, as one unit.

• 친구를 만나요. (Chingureul mannayo.) - [I] meet a friend. English says meet with, Korean does not.
• 버스를 타요. (Beoseureul tayo.) - [I] take the bus. English says get on, so learners expect 에. 버스에 타요 is also correct, but it stresses climbing aboard; for riding a vehicle to get somewhere, 타다 takes 을/를.
• 학교를 다녀요. (Hakgyoreul danyeoyo.) - [I] attend school. English says go to.

Step 4 - 좋아하다 vs 좋다, and 이/가 되다

Two traps that look like one another but pull in opposite directions.

좋아하다 (to like) and 싫어하다 (to dislike) are action verbs, so what you like is the object: 커피를 좋아해요. But 좋다 and 싫다 are descriptive verbs meaning roughly is likeable / is disagreeable, so the thing takes 이/가: 커피가 좋아요. Same English translation, opposite particle.

되다 (to become) goes the other way. English says become a teacher and learners write *선생님을 됐어요; Korean marks the result with 이/가: 선생님이 됐어요.

잘하다 (to be good at) and 못하다 (to be bad at) behave like normal transitive verbs despite the English at: 한국어를 잘해요, 요리를 못해요. Note the spacing - 못하다 written solid means to be bad at, while 못 하다 with a space means cannot do it.

Step 5 - 를 contracts to ㄹ in speech

In conversation and casual writing, 를 collapses onto the previous syllable as a final ㄹ. These are normal, not sloppy:

• 무엇을 / 뭐를 -> 뭘 (mwol). 뭘 마셔요? (Mwol masyeoyo?) - What are you drinking?
• 이것을 -> 이걸 (igeol), 그것을 -> 그걸 (geugeol)
• 저를 -> 절 (jeol), 나를 -> 날 (nal)

Use the full forms in formal writing; recognise the short ones everywhere else.

Step 6 - Dropping the particle

When the role is obvious, everyday speech simply omits 을/를:

• 밥 먹었어요? (Bap meogeosseoyo?) - Have you eaten?
• 물 주세요. (Mul juseyo.) - Water, please.

This is a spoken-register habit, not a licence to drop particles in writing. Keep them in until your ear is reliable.

Step 7 - 하다 compounds can split

공부하다 is one word, but the noun inside it can be pulled out and marked as a real object: 공부를 해요. The split version puts a little weight on the noun (it’s studying that I’m doing). The solid form is the default. Full treatment at 하다 verbs and the noun + 하다 pattern.

Forms & patterns

The allomorph table:

Spoken contractions of 를:

Which particle each verb demands:

하다 compounds, solid vs split:

Examples

Common mistakes

• 사과을 먹어요. (Sagwa-eul meogeoyo.) -> 사과를 먹어요. (Sagwareul meogeoyo.) - 사과 ends in a vowel, so the object particle is 를. 을 only ever follows a 받침.
• 저는 김치가 좋아해요. (Jeoneun gimchiga joahaeyo.) -> 저는 김치를 좋아해요. (Jeoneun gimchireul joahaeyo.) - 좋아하다 is an action verb and takes an object. Only the descriptive 좋다 takes 이/가: 김치가 좋아요.
• 저는 한국어가 잘해요. (Jeoneun Hangugeoga jalhaeyo.) -> 저는 한국어를 잘해요. (Jeoneun Hangugeoreul jalhaeyo.) - English good at hides the object, but 잘하다 is transitive in Korean: what you are good at takes 을/를.
• 저는 선생님을 됐어요. (Jeoneun seonsaengnimeul dwaesseoyo.) -> 저는 선생님이 됐어요. (Jeoneun seonsaengnimi dwaesseoyo.) - 되다 never takes 을/를. The thing you turn into is marked with 이/가.
• 한국어를 공부를 해요. (Hangugeoreul gongbureul haeyo.) -> 한국어를 공부해요. (Hangugeoreul gongbuhaeyo.) - one clause, one object. If 한국어를 is already there, 공부하다 stays solid.

Tips

• Learn the particle as part of the verb, like a German verb’s case. Store it as 친구를 만나다, 버스를 타다, 선생님이 되다 - never as bare 만나다, 타다, 되다. The English translation will lie to you about which particle to use; the memorised chunk will not.
• 좋아하다 is 좋다 turned into an action verb with -아하다, and feeling verbs built this way take objects. That one observation resolves the 좋다/좋아하다 split for good: -아하다/-어하다 -> action -> 을/를; plain 좋다 -> description -> 이/가. Do not stretch it to every 하다 word: 조용하다 (to be quiet) is descriptive.
• ㄹ is a consonant. Learners see 물 or 서울 ending in a “soft” sound and reach for 를. Both take 을: 물을, 서울을.
• Hear the contractions before you use them. 뭘, 이걸 and 절 make you sound natural in speech but out of place in an email or an exam answer, where 무엇을, 이것을 and 저를 belong.