The ㅅ irregular drops its ㅅ before a vowel; the trouble is that most ㅅ-final verbs don't. As with the ㄷ class, the difference is inaudible in the dictionary form — 웃다 ("laugh") and 짓다 ("build") rhyme perfectly and look built the same way, yet 웃다 keeps its ㅅ (웃어요) while 짓다 loses it (지어요). This page fixes the boundary so you stop guessing: it lists the everyday regular ㅅ verbs, and it walks through the single nastiest look-alike pair in the whole system, 낫다 vs 낳다.
The regular ㅅ verbs keep their ㅅ
A regular ㅅ verb behaves like any consonant stem: before a vowel ending, the ㅅ simply liaises forward and reappears as the onset of the next syllable. 웃 + 어요 → 웃어요, pronounced 우서요. Nothing drops.
| Dictionary form | Meaning | 해요 form | Pronounced |
|---|---|---|---|
| 웃다 | laugh / smile | 웃어요 | 우서요 |
| 씻다 | wash | 씻어요 | 씨서요 |
| 벗다 | take off (clothes) | 벗어요 | 버서요 |
| 빗다 | comb | 빗어요 | 비서요 |
| 솟다 | soar / rise up | 솟아요 | 소사요 |
| 빼앗다 | snatch / take away | 빼앗아요 | 빼아사요 |
그 얘기 듣고 다 같이 웃었어요.
geu yaegi deutgo da gachi useosseoyo
We all laughed together when we heard that.
밥 먹기 전에 손 깨끗이 씻어요.
bap meokgi jeone son kkaekkeusi ssiseoyo
Wash your hands well before eating.
집에 오면 제일 먼저 양말을 벗어요.
jibe omyeon jeil meonjeo yangmareul beoseoyo
When I get home, the first thing I do is take off my socks.
친구가 제 장난감을 빼앗아서 울었어요.
chinguga je jangnangameul ppaeasaseo ureosseoyo
My friend snatched my toy, so I cried.
Hear the split directly: the irregular 지어요 ("build") has dropped its ㅅ and left a hiatus, while the regular 씻어요 ("wash") carries its ㅅ straight into the next syllable. Same-looking stems, opposite behavior.
The 낫다 vs 낳다 trap
This is the pair that catches even confident learners, because two different verbs come out sounding exactly the same in their 아/어 form — naayo — while being spelled differently and belonging to different classes.
| Verb | Final consonant | Class | 해요 form | Pronounced |
|---|---|---|---|---|
| 낫다 (heal / be better) | ㅅ | ㅅ irregular — ㅅ drops | 나아요 | 나아요 |
| 낳다 (give birth) | ㅎ | regular ㅎ verb — ㅎ silent, kept in spelling | 낳아요 | 나아요 |
낫다 drops its ㅅ, so it is written 나아요. 낳다 keeps its ㅎ in the spelling — a regular ㅎ verb, not the ㅎ irregular of the color adjectives — but that ㅎ goes silent between vowels, so it is pronounced the same, 나아요. The two are homophones you can only tell apart in writing and by meaning.
약 먹고 푹 쉬면 금방 나아요.
yak meokgo puk swimyeon geumbang naayo
If you take medicine and rest well, you'll get better soon. (heal — 낫다)
옆집 고양이가 새끼를 다섯 마리 낳았어요.
yeopjip goyang-iga saekkireul daseot mari naasseoyo
The cat next door had five kittens. (give birth — 낳다)
The heuristic: memorize the five irregulars, default the rest to regular
There is no audible or spelling clue, so this is rote — but the load is light because the irregular side is a closed list of five. Everything else ending in ㅅ is regular.
- Irregular (ㅅ drops): 짓다, 낫다, 붓다, 잇다, 젓다
- Regular (ㅅ stays): 웃다, 씻다, 벗다, 빗다, 솟다, 빼앗다 — and any other ㅅ verb you meet
Notice the harmony still applies on the regular side too: 솟다 and 빼앗다 have bright vowels (ㅗ, ㅏ), so they take 아 — 솟아요, 빼앗아요.
아침 해가 산 위로 천천히 솟아요.
achim haega san wiro cheoncheonhi sosayo
The morning sun rises slowly over the mountain.
거울을 보면서 머리를 빗어요.
geoureul bomyeonseo meorireul biseoyo
I comb my hair while looking in the mirror.
Common Mistakes
1. Dropping the ㅅ of a regular verb. 웃다 keeps its ㅅ — do not treat it like 짓다.
❌ 아기가 방긋 우어요.
Incorrect — 웃다 is regular; the ㅅ stays: 웃어요.
✅ 아기가 방긋 웃어요.
agiga banggeut useoyo
The baby smiles brightly.
2. Another regular verb over-applied — 씻다.
❌ 자기 전에 얼굴을 시어요.
Incorrect — 씻다 is regular: 씻어요.
✅ 자기 전에 얼굴을 씻어요.
jagi jeone eolgureul ssiseoyo
I wash my face before bed.
3. Keeping the ㅅ of an irregular verb. The mirror error: 짓다 must drop its ㅅ.
❌ 밥을 짓어요.
Incorrect — 짓다 is irregular; the ㅅ drops: 지어요.
✅ 밥을 지어요.
babeul jieoyo
I cook rice.
4. Spelling "give birth" as if it were 낫다. They sound alike, but the ㅎ is part of 낳다.
❌ 언니가 어제 아들을 나았어요.
Incorrect for 'give birth' — that's the spelling of 낫다 'heal'. Give birth = 낳았어요.
✅ 언니가 어제 아들을 낳았어요.
eonniga eoje adeureul naasseoyo
My older sister had a son yesterday.
5. The reverse — spelling "heal" with a ㅎ.
❌ 상처가 다 낳았어요.
Incorrect for 'heal' — 낳다 means 'give birth'. Heal = 나았어요.
✅ 상처가 다 나았어요.
sangcheoga da naasseoyo
The wound has completely healed.
Key Takeaways
- Most ㅅ-final verbs are regular — the ㅅ liaises forward and stays (웃어요, 씻어요, 벗어요).
- Only the five irregulars (짓다, 낫다, 붓다, 잇다, 젓다) drop their ㅅ; default every other ㅅ verb to regular.
- 낫다 (heal, ㅅ drops → 나아요) and 낳다 (give birth, ㅎ silent → 낳아요) are homophones — identical sound, different spelling and class.
- Membership is inaudible and invisible in the dictionary form, so memorize each verb by its 해요 form.
- Vowel harmony still runs on both sides: 솟다 → 솟아요, 짓다 → 지어요.
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Start learning Korean→Related Topics
- The ㅅ Irregular: 짓다 → 지어요 (and Why It Doesn't Contract)TOPIK 2 — Stem-final ㅅ simply drops before a vowel- or 으-initial ending — 짓다 → 지어요, 나아요, 부어요 — and uniquely leaves a two-vowel hiatus that must NOT contract to 져요.
- Irregular Predicates at a Glance (Reference Table)TOPIK 2 — One-screen reference for all eight irregular classes — the trigger, the change, a model verb with its 아/어-form and 으-form, and a regular look-alike to guard against over-generalizing each class.
- ㅎ Color Adjectives (파랗다 → 파래요) and Regular ㅎ Verbs (좋다)TOPIK 2 — Every ㅎ-final color adjective is irregular — 파랗다 → 파래요/파란, 하얗다 → 하얘요/하얀 — but ㅎ-final verbs (넣다, 놓다, 낳다) are regular and keep their ㅎ. The split runs almost cleanly by part of speech, with 좋다 as the lone regular ㅎ-adjective, plus the notorious 낳다-vs-낫다 spelling trap.
- ㄷ Homograph Traps and Regular ㄷ VerbsTOPIK 2 — Why 걷다 and 묻다 each split into an irregular and a regular verb by meaning, and the common ㄷ verbs (받다, 닫다, 믿다…) that keep their ㄷ before every ending.