으-Drop Verbs (으 탈락): Full Table | Korean Grammar

The 으-drop (으 탈락) sits in the "irregular" chapter under false pretenses: it is actually the most predictable conjugation in Korean. The rule is one line — any stem whose final vowel is ㅡ loses that ㅡ before an 아/어 ending — and unlike the genuinely lexical ㅂ, ㄷ, and ㅅ classes, there are no exceptions to memorize. Every ㅡ-final stem does it. This page is the paradigm grid, organized by the one thing that varies — which harmony vowel surfaces after the ㅡ leaves. (For the harmony logic in fuller depth, see the companion ㅡ-drop harmony table.)

The one-line rule behind the grid

A bare ㅡ has no harmony value of its own — it is neither bright nor dark. So when an 아/어 ending arrives, the ㅡ simply deletes, the leftover consonant re-attaches as the onset of the ending's syllable, and harmony is decided by the vowel one syllable back:

preceding vowel ㅏ or ㅗ → 아 (바빠, 아파, 모아),
anything else, or no preceding syllable at all → 어 (예뻐, 커, 써).

The 으 drops only before 아/어. Before consonant endings and 으-endings the stem is intact, and — because a ㅡ stem is vowel-final — it takes no 으 buffer (쓰면, 쓰세요, 씁니다).

💡

Two-step it every time: (1) delete the final ㅡ, (2) read the vowel one syllable back to pick 아 or 어. Single-syllable stems (크-, 쓰-, 끄-) have nothing behind them, so they default to 어 → 커, 써, 꺼 — never ×카, ×싸, ×까. The ㅡ is a blank that deletes and passes the harmony choice backward.

Band 1 — one-syllable stems (no preceding vowel → default 어)

With nothing behind the ㅡ, harmony has nothing to work on, so these always take 어.

Dictionary (meaning)	해요체 -아/어요	Past -았/었어요	-아서/어서
쓰다 (write / use)	써요 sseoyo	썼어요 sseosseoyo	써서 sseoseo
크다 (be big / tall)	커요 keoyo	컸어요 keosseoyo	커서 keoseo
끄다 (turn off)	꺼요 kkeoyo	껐어요 kkeosseoyo	꺼서 kkeoseo

여기에 성함을 좀 써 주세요.

yeogie seonghameul jom sseo juseyo

Please write your name here. (쓰다 → 써)

몇 년 사이에 애들이 정말 많이 컸어요.

myeot nyeon saie aedeuri jeongmal mani keosseoyo

The kids have grown so much in just a few years. (크다 → 컸어요)

깜빡하고 불을 안 꺼서 다시 집에 갔어요.

kkamppakago bureul an kkeoseo dasi jibe gasseoyo

I forgot to turn off the light, so I went back home. (끄다 → 꺼서)

Band 2 — preceding vowel ㅏ or ㅗ (→ 아)

When the syllable before the ㅡ carries a bright vowel, the ending is 아.

Dictionary (meaning)	해요체 -아/어요	Past -았/었어요	-아서/어서
아프다 (be sick / hurt)	아파요 apayo	아팠어요 apasseoyo	아파서 apaseo
바쁘다 (be busy)	바빠요 bappayo	바빴어요 bappasseoyo	바빠서 bappaseo
나쁘다 (be bad)	나빠요 nappayo	나빴어요 nappasseoyo	나빠서 nappaseo
배고프다 (be hungry)	배고파요 baegopayo	배고팠어요 baegopasseoyo	배고파서 baegopaseo
모으다 (gather / save)	모아요 moayo	모았어요 moasseoyo	모아서 moaseo

Note that 모으다 belongs here, not in the "dark" band: the syllable before its ㅡ is 모 (ㅗ, bright), so it takes 아 → 모아요. Read the vowel immediately before the ㅡ — in 배고프다 that is 고 (ㅗ), which is why it is 배고파요 and not ×배고퍼요.

아침부터 목이 좀 아파요.

achimbuteo mogi jom apayo

My throat's been a little sore since this morning. (아프다 → 아파요)

요즘 일이 너무 바빠서 연락도 못 했어요.

yojeum iri neomu bappaseo yeollakdo mot haesseoyo

I've been so swamped lately that I couldn't even get in touch. (바쁘다 → 바빠서)

일 년 동안 용돈을 모아서 노트북을 샀어요.

il nyeon dong-an yongdoneul moaseo noteubugeul sasseoyo

I saved up my allowance for a year and bought a laptop. (모으다 → 모아서)

Band 3 — preceding vowel is anything else (→ 어)

If the syllable before the ㅡ has a non-bright vowel (ㅕ, ㅣ, ㅡ, and the rest), the ending is 어.

Dictionary (meaning)	해요체 -아/어요	Past -았/었어요	-아서/어서
예쁘다 (be pretty)	예뻐요 yeppeoyo	예뻤어요 yeppeosseoyo	예뻐서 yeppeoseo
기쁘다 (be glad)	기뻐요 gippeoyo	기뻤어요 gippeosseoyo	기뻐서 gippeoseo
슬프다 (be sad)	슬퍼요 seulpeoyo	슬펐어요 seulpeosseoyo	슬퍼서 seulpeoseo

예쁘다's preceding vowel is ㅕ (in 예), which is not bright, so it is 예뻐요 — even though the ㅃ and the ㅕ might tempt you toward 아. Harmony reads the vowel, not the feel of the syllable.

이 카페 분위기가 너무 예뻐요.

i kape bunwigiga neomu yeppeoyo

This café's whole vibe is so pretty. (예쁘다 → 예뻐요)

합격 소식을 듣고 너무 기뻐서 눈물이 났어요.

hapgyeok sosigeul deutgo neomu gippeoseo nunmuri nasseoyo

I was so glad to hear I passed that I teared up. (기쁘다 → 기뻐서)

어제 본 영화 결말이 너무 슬펐어요.

eoje bon yeonghwa gyeolmari neomu seulpeosseoyo

The ending of the movie I watched yesterday was so sad. (슬프다 → 슬펐어요)

Nothing happens before other endings

The ㅡ drops only before 아/어. Before a consonant ending, or before an 으-ending, the stem stays whole — and because it is vowel-final, no 으 is inserted.

시험이니까 볼펜으로 쓰면 안 돼요.

siheominikka bolpeneuro sseumyeon an dwaeyo

It's an exam, so you mustn't write in ballpoint. (쓰다 → 쓰면, ㅡ kept, no 으 buffer)

저는 일기를 매일 씁니다.

jeoneun ilgireul maeil sseumnida

I write in my diary every day. (formal; 쓰다 → 씁니다, vowel stem takes -ㅂ니다)

Why this is the "regular" irregular — and where 르 splits off

Korea's genuinely irregular classes are lexical: some ㅂ-stems flip to 우 (돕다 → 도와) and others, spelled identically, do not (좁다 → 좁아), so you must memorize membership verb by verb. The 으-drop is nothing like that — every ㅡ-final stem drops the ㅡ before 아/어, with not a single holdout. That makes it a phonological rule, closer to English "a → an before a vowel" than to "sing → sang." For an English speaker the useful reframe is this: English silent-vowel drops (the e in make → making) are spelling conventions, but the Korean ㅡ-drop is a live sound rule with a twist — the vanishing vowel hands the harmony decision to its neighbor. That is the whole reason 바빠 and 예뻐 differ: same rule, different neighbor.

The one boundary to respect: stems ending in 르 (모르다, 다르다, 부르다) are a doubling sub-case layered on top of the ㅡ-drop — they drop the 으 and copy a ㄹ back (모르다 → 몰라요, not ×모러요). That is the separate 르-irregular. Everything on this page is the plain drop — 쁘, 프, 쓰, 크, 으 — but not 르.

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Zero exceptions to fear: the moment you see a ㅡ in the last syllable of a stem, the 아/어 form writes itself. The only thing to double-check is which vowel one syllable back — and if there is none, it's 어. The single trap is 르-stems, which double the ㄹ instead.

Common Mistakes

1. Keeping the ㅡ before 아/어. The ㅡ must drop.

❌ 여기에 이름을 쓰어요.

Wrong — the ㅡ of 쓰- drops before 어: 써요.

✅ 여기에 이름을 써요.

yeogie ireumeul sseoyo

Write your name here.

2. Defaulting a one-syllable ㅡ stem to 아. With no preceding vowel, the ending is always 어.

❌ 나갈 때 불 좀 까 주세요.

Wrong — 끄다 → 꺼 (single-syllable ㅡ always takes 어); 까 is from 까다 'to peel'.

✅ 나갈 때 불 좀 꺼 주세요.

nagal ttae bul jom kkeo juseyo

Please turn off the light when you leave.

3. Reading harmony off the wrong syllable. Read the vowel just before the ㅡ.

❌ 요즘 너무 바뻐요.

Wrong — the vowel before ㅡ is ㅏ (in 바), which is bright → 아: 바빠요.

✅ 요즘 너무 바빠요.

yojeum neomu bappayo

I'm so busy these days.

4. Inserting an 으 buffer before -면. A vowel-final ㅡ stem takes plain -면.

❌ 볼펜으로 쓰으면 안 돼요.

Wrong — no 으 on a ㅡ stem; it's 쓰면.

✅ 볼펜으로 쓰면 안 돼요.

bolpeneuro sseumyeon an dwaeyo

You mustn't write in ballpoint pen.

5. Treating a 르-stem as a plain 으-drop. 르-stems double the ㄹ.

❌ 저는 그 사람 이름을 모러요.

Wrong — 모르다 is the 르-irregular: 몰라요, not a plain ㅡ-drop.

✅ 저는 그 사람 이름을 몰라요.

jeoneun geu saram ireumeul mollayo

I don't know that person's name.

Key Takeaways

Any stem whose last vowel is ㅡ drops it before an 아/어 ending: 쓰다 → 써요, 아프다 → 아파요, 예쁘다 → 예뻐요.
Harmony is set by the vowel one syllable back: bright (ㅏ/ㅗ) → 아 (바빠, 모아); otherwise, or if none, → 어 (예뻐, 커).
Single-syllable ㅡ stems always default to 어 (커, 써, 꺼) — never 아.
The ㅡ drops only before 아/어; before consonant/으-endings it stays and takes no 으 buffer (쓰면, 씁니다).
This is a fully regular phonological rule with zero lexical exceptions — the only twist is that 르-stems double the ㄹ (모르다 → 몰라요) and belong to the 르-irregular.

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