A whole second family of endings — the "modal/attaching" endings like -(으)세요, -(으)면, -(으)니까, -(으)ㄹ, -(으)ㄴ — is written with a -(으) in parentheses. That 으 is not part of the ending. It is an epenthetic buffer vowel: it appears only when a consonant batchim would otherwise crash straight into the ending, and it vanishes after a vowel stem. A third case, the ㄹ-stem, drops its ㄹ instead of ever showing 으. This page is the lookup grid for all three.
The rule
- Consonant-final stem (먹-, 읽-, 앉-) → 으 appears as a buffer: 먹으세요, 먹으면, 먹은.
- Vowel-final stem (가-, 오-, 마시-) → no 으 (the ending attaches straight onto the vowel): 가세요, 가면, 간.
- ㄹ-final stem (살-, 알-, 놀-) → never shows 으; instead the ㄹ drops before ㄴ, ㅅ, ㅂ and the future ㄹ (사세요, 산, 삽시다), but stays before ㅁ-initial 면 (살면).
The reframing English speakers need: 으 is written in parentheses precisely because it is conditional. It is not a piece of the ending you memorize; it is a hiccup vowel that only shows up after a batchim to keep two consonants from colliding. That is exactly why 가세요 has no 으 but 먹으세요 does.
The insertion table
| Ending | Consonant stem 먹- | Vowel stem 가- | ㄹ-stem 살- |
|---|---|---|---|
| -(으)세요 (polite request) | 먹으세요 | 가세요 | 사세요 (ㄹ drops) |
| -(으)면 (if) | 먹으면 | 가면 | 살면 (ㄹ stays) |
| -(으)니까 (because) | 먹으니까 | 가니까 | 사니까 (ㄹ drops) |
| -(으)러 (in order to) | 먹으러 | 가러 | 살러 (ㄹ stays) |
| -(으)ㄴ (past attributive) | 먹은 | 간 | 산 (ㄹ drops) |
| -(으)ㄹ (prospective) | 먹을 | 갈 | 살 (ㄹ merges) |
| -(으)ㅂ시다 (let's, formal) | 먹읍시다 | 갑시다 | 삽시다 (ㄹ drops) |
| -(으)ㄹ까요 (shall we?) | 먹을까요 | 갈까요 | 살까요 (ㄹ merges) |
| -(으)십니다 (honorific, formal) | 먹으십니다 | 가십니다 | 사십니다 (ㄹ drops) |
| -(으)ㄹ 수 있다 (can) | 먹을 수 있다 | 갈 수 있다 | 살 수 있다 (ㄹ merges) |
Read down any column and the pattern is airtight. The consonant column always shows 으; the vowel column never does; the ㄹ column never shows 으 either — it just decides whether the ㄹ survives, and that depends only on the first sound of the ending.
The ㄹ-stem sub-rule: drop before ㄴ ㅅ ㅂ ㄹ
The ㄹ-stem row is the one place learners stumble, so isolate its logic. A stem-final ㄹ deletes before an ending that begins with ㄴ, ㅅ, ㅂ, or the prospective ㄹ (the classic "ㄴㅅㅂㄹ" set); before any other consonant — notably ㅁ in -면 — the ㄹ stays. Crucially, a ㄹ-stem never inserts 으: 으 is a buffer for a consonant that has nowhere to go, but ㄹ resolves the clash by dropping, so no buffer is ever needed.
여기 앉으세요.
yeogi anjeuseyo
Please sit here. (앉- consonant stem → 으 inserted: 앉으세요)
이거 다 드시고 천천히 가세요.
igeo da deusigo cheoncheonhi gaseyo
Finish this and head off slowly. (가- vowel stem → no 으: 가세요)
할머니는 시골에서 사세요.
halmeonineun sigoreseo saseyo
My grandmother lives in the countryside. (살- ㄹ-stem, ㅅ ending → ㄹ drops: 사세요)
으 appears after a batchim
시간 있으면 커피 한잔 할까요?
sigan isseumyeon keopi hanjan halkkayo?
If you've got time, shall we grab a coffee? (있- → 있으면)
배가 고프니까 뭐 좀 먹으러 가요.
baega gopeunikka mwo jom meogeureo gayo
I'm hungry, so let's go grab something to eat. (먹- → 먹으러)
지난주에 읽은 책이 정말 재미있었어요.
jinanjue ilgeun chaegi jeongmal jaemiisseosseoyo
The book I read last week was really interesting. (읽- → 읽은)
No 으 after a vowel — and never in a ㄹ-stem
주말에 시간 되면 같이 등산 가요.
jumare sigan doemyeon gachi deungsan gayo
If you're free on the weekend, let's go hiking. (되- vowel stem → 되면, no 으)
서울에 살면 지하철이 정말 편해요.
Seoure salmyeon jihacheori jeongmal pyeonhaeyo
If you live in Seoul, the subway is really convenient. (살- + 면 → 살면, ㄹ stays)
Reframing for English speakers
There is no English analog for a vowel that exists only to prevent a consonant collision, but the logic is familiar from the a/an alternation: an apple, a pear — the extra n appears only where the following sound needs it. 으 works the same way, inserted after a batchim purely for pronounceability and skipped where the sounds already flow. So do not memorize 으 as "the front of the ending." Memorize the ending as -(으)ㄴ, -(으)면, -(으)세요 — parentheses and all — and let the batchim decide whether the 으 surfaces.
Common Mistakes
1. Inserting 으 after a vowel stem. Vowel stems attach the ending directly.
❌ 조심해서 천천히 가으세요.
Wrong — 가- is a vowel stem, no 으: 가세요.
✅ 조심해서 천천히 가세요.
josimhaeseo cheoncheonhi gaseyo
Take care and go slowly.
2. Keeping 으 in a ㄹ-stem. ㄹ-stems drop the ㄹ (or keep it) but never take 으.
❌ 서울에 살으면 편해요.
Wrong — 살- is a ㄹ-stem; before -면 the ㄹ stays and there is no 으: 살면.
✅ 서울에 살면 편해요.
Seoure salmyeon pyeonhaeyo
If you live in Seoul, it's convenient.
3. Failing to drop ㄹ before ㄴ. The past attributive -(으)ㄴ drops the ㄹ.
❌ 서울에 살은 사람.
Wrong — the ㄹ of 살- drops before -ㄴ: 산 사람.
✅ 서울에 산 사람.
Seoure san saram
a person who has lived in Seoul
4. Dropping the 으 after a consonant stem. A batchim needs the buffer.
❌ 이 약을 자기 전에 먹세요.
Wrong — 먹- is a consonant stem, so 으 is required: 먹으세요.
✅ 이 약을 자기 전에 먹으세요.
i yageul jagi jeone meogeuseyo
Take this medicine before bed.
Key Takeaways
- 으 is an epenthetic buffer: it surfaces only between a consonant batchim and a -(으) ending (먹으면), and is absent after a vowel stem (가면).
- The 으 is written in parentheses because it is conditional — it is not part of the ending.
- ㄹ-stems never take 으. The ㄹ drops before ㄴ/ㅅ/ㅂ and the prospective ㄹ (사세요, 산, 삽시다, 살), but stays before -면 (살면).
- Endings carrying -(으): -(으)세요, -(으)면, -(으)니까, -(으)러, -(으)ㄴ, -(으)ㄹ, -(으)ㅂ시다, -(으)ㄹ까요, -(으)십니다, -(으)ㄹ 수 있다.
- The two errors to kill: ×가으세요 (으 after a vowel) and ×살으면 / ×살은 (으 kept in a ㄹ-stem).
Now practice Korean
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Start learning Korean→Related Topics
- 살다 (to live): ㄹ-Stem Verb ParadigmTOPIK 2 — The complete look-up paradigm of 살다 across all four speech levels — the model for ㄹ-stem verbs, whose stem ㄹ drops before ㄴ, ㅂ, ㅅ, and 시, stays everywhere else, and never takes the 으 buffer.
- 먹다 (to eat): Consonant-Stem Verb ParadigmTOPIK 1 — The complete look-up paradigm of 먹다 across all four speech levels — the stencil for every regular consonant-stem action verb, with the obligatory 으 buffer that batchim stems insert before consonant-initial endings.
- The ㅡ-Drop (으 탈락) TableTOPIK 2 — A fully regular alternation: a stem whose final vowel is ㅡ drops it before any 아/어 ending, and the syllable before the dropped ㅡ then decides harmony — 바쁘다→바빠, 예쁘다→예뻐, 크다→커. The 르-stems are a separate irregular.
- ㄹ-Stems: The Disappearing ㄹ (살다 → 삽니다, 사세요)TOPIK 1 — Stems ending in ㄹ (살다, 알다, 만들다) drop that ㄹ before endings starting in ㄴ, ㅂ, ㅅ and before -(으) forms — a fully rule-governed elision, not a random irregularity, and distinct from the seven true irregular classes.