Overview
The ㅅ irregular (ㅅ 불규칙) affects certain verbs whose stems end in ㅅ. When these verbs are followed by a vowel-starting ending, the ㅅ simply drops — it disappears completely.
| Type | Before vowel ending | Example |
|---|---|---|
| Regular ㅅ | ㅅ stays | 웃다 → 웃어요 |
| Irregular ㅅ | ㅅ drops | 짓다 → 지어요 |
The rule: In irregular ㅅ verbs, the ㅅ disappears before vowel endings. Nothing replaces it.
The Rule
Before vowel endings: ㅅ drops
| Verb | Stem | ㅅ drops | + ending | Result |
|---|---|---|---|---|
| 짓다 (build) | 짓 | 지 | + 어요 | 지어요 |
| 낫다 (recover) | 낫 | 나 | + 아요 | 나아요 |
| 붓다 (pour) | 붓 | 부 | + 어요 | 부어요 |
| 긋다 (draw a line) | 긋 | 그 | + 어요 | 그어요 |
| 잇다 (connect) | 잇 | 이 | + 어요 | 이어요 |
Note: Unlike the ㅂ irregular (where ㅂ is replaced by 우), the ㅅ irregular simply removes ㅅ with no replacement.
Before consonant endings: No change
| Verb | + 고 | + 지만 | + ㅂ니다 |
|---|---|---|---|
| 짓다 | 짓고 | 짓지만 | 짓습니다 |
| 낫다 | 낫고 | 낫지만 | 낫습니다 |
| 붓다 | 붓고 | 붓지만 | 붓습니다 |
Common Irregular ㅅ Verbs
| Dictionary | Meaning | 해요체 | Past | Future |
|---|---|---|---|---|
| 짓다 | build, make, name | 지어요 | 지었어요 | 지을 거예요 |
| 낫다 | recover, get better | 나아요 | 나았어요 | 나을 거예요 |
| 붓다 | pour, swell | 부어요 | 부었어요 | 부을 거예요 |
| 긋다 | draw (a line) | 그어요 | 그었어요 | 그을 거예요 |
| 잇다 | connect, continue | 이어요 | 이었어요 | 이을 거예요 |
| 젓다 | stir, row | 저어요 | 저었어요 | 저을 거예요 |
There are relatively few ㅅ irregular verbs. 짓다 and 낫다 are by far the most commonly used.
Regular ㅅ Verbs (NOT Irregular)
These verbs end in ㅅ but conjugate regularly — ㅅ stays:
| Dictionary | Meaning | 해요체 | Why regular |
|---|---|---|---|
| 웃다 | laugh, smile | 웃어요 | ㅅ stays |
| 씻다 | wash | 씻어요 | ㅅ stays |
| 벗다 | take off (clothes) | 벗어요 | ㅅ stays |
| 빼앗다 | snatch | 빼앗아요 | ㅅ stays |
Pattern hint: Most verbs with a double consonant cluster before ㅅ (like 씻, 벗) tend to be regular. But this is not a guaranteed rule — you must memorize which are irregular.
Full Conjugation Table
짓다 (to build, to make, to name)
| Form | Conjugation | Notes |
|---|---|---|
| 해요체 | 지어요 | ㅅ drops + 어요 |
| Past | 지었어요 | ㅅ drops + 었어요 |
| Future | 지을 거예요 | ㅅ drops + 을 거예요 |
| ~(으)면 | 지으면 | ㅅ drops + 으면 |
| ~(으)니까 | 지으니까 | ㅅ drops + 으니까 |
| ~(으)세요 | 지으세요 | ㅅ drops + 으세요 |
| Formal | 짓습니다 | Consonant ending: no change |
| ~고 | 짓고 | Consonant ending: no change |
| ~지만 | 짓지만 | Consonant ending: no change |
낫다 (to get better, to recover)
| Form | Conjugation | Notes |
|---|---|---|
| 해요체 | 나아요 | ㅅ drops + 아요 (ㅏ vowel) |
| Past | 나았어요 | ㅅ drops + 았어요 |
| Future | 나을 거예요 | ㅅ drops + 을 거예요 |
| ~(으)면 | 나으면 | ㅅ drops + 으면 |
| Formal | 낫습니다 | Consonant ending: no change |
| ~고 | 낫고 | Consonant ending: no change |
Example Sentences
새 집을 지었어요. (I built a new house.)
아기 이름을 지어 주세요. (Please name the baby.)
감기가 빨리 나았으면 좋겠어요. (I hope my cold gets better soon.)
어제보다 나아요. (It's better than yesterday.)
컵에 물을 부어 주세요. (Please pour water into the cup.)
다리가 부었어요. (My leg is swollen.) — 붓다 also means "to swell"
선을 그었어요. (I drew a line.)
국을 저어 주세요. (Please stir the soup.)
Regular ㅅ verbs for comparison
재미있어서 웃었어요. (It was funny so I laughed.) — 웃다 is regular
손을 씻어요. (I wash my hands.) — 씻다 is regular
Comparing All ㅅ-Final Verbs
| Verb | Meaning | Irregular? | 해요체 |
|---|---|---|---|
| 짓다 | build | Yes | 지어요 |
| 낫다 | recover | Yes | 나아요 |
| 붓다 | pour/swell | Yes | 부어요 |
| 긋다 | draw line | Yes | 그어요 |
| 잇다 | connect | Yes | 이어요 |
| 젓다 | stir | Yes | 저어요 |
| 웃다 | laugh | No | 웃어요 |
| 씻다 | wash | No | 씻어요 |
| 벗다 | take off | No | 벗어요 |
Common Mistakes
| Mistake | Correction | Why |
|---|---|---|
| 짓어요 | 지어요 | ㅅ drops before vowel endings |
| 낫아요 | 나아요 | ㅅ drops: 낫 → 나 + 아요 |
| 웃어요 → 우어요 | 웃어요 is correct | 웃다 is regular, ㅅ stays |
| 지고 | 짓고 | Before consonant endings, ㅅ stays |
| 붓어요 | 부어요 | ㅅ drops: 붓 → 부 + 어요 |
Summary
- In ㅅ irregular verbs, the ㅅ drops completely before vowel endings (nothing replaces it).
- Before consonant endings (~고, ~지만, ~ㅂ니다), ㅅ stays unchanged.
- The most important irregular ㅅ verbs are: 짓다 (build/name), 낫다 (recover), 붓다 (pour/swell).
- Common regular ㅅ verbs include: 웃다 (laugh), 씻다 (wash), 벗다 (take off).
- There are relatively few ㅅ irregular verbs, making them manageable to memorize.
- Remember: ㅅ drops with nothing replacing it — this is unique compared to ㅂ (→ 우) or ㄷ (→ ㄹ) irregulars.