Ending Attachment After Batchim (받침 이형태): Allomorphy Reference | Korean Grammar

Almost every particle and ending in Korean comes in two shapes, and choosing between them looks like a lot of separate rules to memorize: 이 or 가? 을 or 를? -으면 or -면? -으세요 or -세요? In fact it is one rule wearing many costumes. A Korean stem or noun either ends in a vowel or ends in a 받침 (batchim, a final consonant), and that single fact decides every one of these choices. After a batchim, Korean adds a helper — the vowel 으, or the consonant-heavy allomorph 은/을/이. After a vowel, it adds nothing extra, because the two sounds already glide together. This page is the master reference: one table showing the pattern across all the major particles and endings, plus the special behaviour of ㄹ.

The allomorphy table

The left column pairs each ending's after-vowel and after-consonant shapes. Read the example pair as vowel-stem / consonant-stem.

Ending	After vowel	After consonant	Example pair (V / C)
Subject	가	이	친구가 / 책이 (chinguga / chaegi)
Object	를	을	사과를 / 밥을 (sagwareul / babeul)
Topic	는	은	나는 / 집은 (naneun / jibeun)
Instrument	로	으로	버스로 / 손으로 (beoseuro / soneuro)
Comitative	와	과	친구와 / 학생과 (chinguwa / haksaenggwa)
Conditional "if"	-면	-으면	가면 / 먹으면 (gamyeon / meogeumyeon)
Polite imperative	-세요	-으세요	가세요 / 읽으세요 (gaseyo / ilgeuseyo)
Reason "since"	-니까	-으니까	오니까 / 먹으니까 (onikka / meogeunikka)
Past-modifier	-ㄴ	-은	간 / 먹은 (gan / meogeun)
Future-modifier	-ㄹ	-을	갈 / 먹을 (gal / meogeul)

Notice that the whole right column shares one insertion: 으 (or the 으-containing 은/을/이). That is the only thing being added after a consonant, and it exists for a purely mechanical reason — to keep the cluster pronounceable. 먹 + ㄴ would jam two consonants together, so Korean slots in 으 to make 먹은; 가 + ㄴ already ends in a vowel, so the ㄴ attaches bare as 간. The comitative pair 와/과 is the one that runs backwards (와 after a vowel, 과 after a consonant), so keep an eye on it.

💡

Collapse every row into one instruction: after a batchim, add 으 (or 은 / 을 / 이); after a vowel, attach the bare ending. If you can hear that a form would be hard to say without a helper vowel, that is exactly where 으 goes.

The rule in motion

The point of a single underlying rule is that you stop memorizing particles one by one and start hearing where the buffer belongs. A stem ending in a vowel takes the light form; a stem ending in a consonant takes the heavy one.

시간 있으면 잠깐 얘기 좀 해요.

sigan isseumyeon jamkkan yaegi jom haeyo

If you have time, let's talk for a bit. (consonant stem 있다 → 있으면)

이 약을 먹으면 좀 나을 거예요.

i yageul meogeumyeon jom naeul geoyeyo

If you take this medicine you'll feel better. (consonant stem 먹다 → 먹으면)

오늘은 시간이 없으니까 내일 만나요.

oneureun sigani eopseunikka naeil mannayo

I'm out of time today, so let's meet tomorrow. (consonant stem 없다 → 없으니까)

여기 앉으세요.

yeogi anjeuseyo

Please have a seat here. (double-batchim stem 앉다 → 앉으세요)

ㄹ behaves half like a vowel

The one stem that breaks the neat vowel/consonant split is the ㄹ-final one, and it breaks it in a consistent way: ㄹ never takes 으. A noun ending in ㄹ takes the vowel-side instrument 로 (연필로, not ×연필으로), exactly as if it ended in a vowel. And a ㄹ-stem verb attaches the -(으) endings with the 으 dropped: 살다 → 사니까 (not ×살으니까), 사세요, 산. On top of that, the ㄹ itself disappears before ㄴ / ㅅ / ㅂ-initial endings — a further quirk covered on the ㄹ-irregular page — but it survives before ㅁ (살다 → 살면, ㄹ intact). Treat ㄹ as a consonant that thinks it is a vowel.

문을 열면 바람이 들어와요.

muneul yeolmyeon barami deureowayo

If you open the door, the wind comes in. (ㄹ-stem 열다 → 열면, ㄹ kept before ㅁ, no 으)

여기 오래 사니까 이제 익숙해요.

yeogi orae sanikka ije iksukaeyo

Since I've lived here a long time, I'm used to it now. (ㄹ-stem 살다 → 사니까, ㄹ dropped, no 으)

볼펜으로 쓰세요, 연필로 쓰지 마세요.

bolpeneuro sseuseyo, yeonpillo sseuji maseyo

Write with a pen, don't write with a pencil. (으로 after ㄴ vs 로 after ㄹ, in one sentence)

The other consonant to watch: 으-stems

A separate stem type looks like it should trigger 으-insertion but does the opposite. A verb whose stem ends in the vowel ㅡ — 쓰다 (write), 크다 (big), 바쁘다 (busy) — counts as a vowel stem, so it takes bare endings and even drops its own ㅡ before -아/어 (쓰다 → 써요). Don't confuse an 으-stem (vowel-final) with a batchim stem. The 으-drop page covers this fully.

이름을 여기에 쓰면 돼요.

ireumeul yeogie sseumyeon dwaeyo

You can write your name here. (으-stem 쓰다 counts as a vowel stem → 쓰면, no extra 으)

Common Mistakes

1. Adding 으 after a vowel stem. A vowel stem takes the bare ending — no buffer.

❌ 지금 집에 가으니까 나중에 전화할게요.

Wrong — 가다 is a vowel stem, so it's 가니까, not 가으니까.

✅ 지금 집에 가니까 나중에 전화할게요.

jigeum jibe ganikka najunge jeonhwahalgeyo

I'm heading home now, so I'll call you later.

2. Adding 으 after a ㄹ-stem. ㄹ refuses the buffer; the 으 drops out entirely.

❌ 서울에 살으니까 자주 못 만나요.

Wrong — ㄹ-stem 살다 drops both the ㄹ and the 으: 사니까.

✅ 서울에 사니까 자주 못 만나요.

Seoure sanikka jaju mot mannayo

I live in Seoul, so we can't meet often.

3. Using 으로 after a ㄹ-final noun. After ㄹ, instrument is 로.

❌ 지하철으로 갈 거예요.

Wrong — 지하철 ends in ㄹ, so it takes 로: 지하철로.

✅ 지하철로 갈 거예요.

jihacheollo gal geoyeyo

I'll go by subway.

4. Dropping the buffer after a real consonant stem. A batchim stem needs the 으.

❌ 이거 다 읽면 알려 주세요.

Wrong — 읽다 ends in a consonant cluster, so the buffer is required: 읽으면.

✅ 이거 다 읽으면 알려 주세요.

igeo da ilgeumyeon allyeo juseyo

Let me know when you've finished reading all this.

Key Takeaways

One rule underlies all the two-shape particles and endings: after a batchim, add 으 (or 은 / 을 / 이); after a vowel, attach the bare ending.
The buffer 으 exists only for pronounceability — to break an otherwise unpronounceable consonant cluster.
ㄹ behaves half like a vowel: it never takes 으 (연필로, 사니까), though the ㄹ itself drops before ㄴ / ㅅ / ㅂ and survives before ㅁ (살면).
The comitative pair runs backwards: 와 after a vowel, 과 after a consonant.
An 으-stem (쓰다, 크다) is a vowel stem — it takes bare endings, not the 으-buffer.

Now practice Korean

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

Start learning Korean→