ㅅ irregular verbs (ㅅ 불규칙) are verbs and adjectives whose stem ends in ㅅ and drop this final consonant when followed by vowel-starting endings.
What Makes Them Irregular
Regular verbs maintain their stem throughout conjugation. ㅅ irregular verbs completely drop the final ㅅ before vowel-starting endings.
Rule
When ㅅ stem meets vowel-starting endings:
- The ㅅ drops completely before vowel endings (-아/어, -으면, -을)
- ㅅ is kept before consonant-starting endings (-습니다, -지, -고)
Common ㅅ Irregular Verbs
Most ㅅ irregular words are adjectives:
- 낫다 (natda) - to be better, to recover
- 짓다 (jitda) - to build, to make
- 붓다 (butda) - to swell, to pour
- 긋다 (geutda) - to draw (a line)
Note: There are very few ㅅ irregular verbs/adjectives in modern Korean.
Conjugation Pattern
Pattern 1: ㅅ Drops Before -어/아
낫다 (to be better/recover):
- 낫 + 아요 → 나아요 (ㅅ drops)
- Stem vowel is ㅏ, so uses -아
짓다 (to build):
- 짓 + 어요 → 지어요 (ㅅ drops)
- Stem vowel is ㅣ, so uses -어
붓다 (to swell):
- 붓 + 어요 → 부어요 (ㅅ drops)
- Stem vowel is ㅜ, so uses -어
긋다 (to draw a line):
- 긋 + 어요 → 그어요 (ㅅ drops)
- Stem vowel is ㅡ, so uses -어
Pattern 2: ㅅ Kept Before Consonants
Before -습니다:
- 낫다 → 낫습니다 (is better - formal)
- 짓다 → 짓습니다 (build - formal)
- 붓다 → 붓습니다 (swell - formal)
Before -지:
- 낫다 → 낫지 않아요 (not better)
- 짓다 → 짓지 마세요 (don't build)
Before -고:
- 낫다 → 낫고 (is better and)
- 짓다 → 짓고 (build and)
Pattern 3: ㅅ Drops Before -(으)ㄴ/ㄹ
Modifiers -(으)ㄴ:
- 낫다 → 나은 (better)
- 짓다 → 지은 (built)
- 붓다 → 부은 (swollen)
Future modifier -(으)ㄹ:
- 낫다 → 나을 (will be better)
- 짓다 → 지을 (will build)
- 붓다 → 부을 (will swell)
Pattern 4: ㅅ Drops Before -(으)면
Conditional:
- 낫다 → 나으면 (if better)
- 짓다 → 지으면 (if build)
- 붓다 → 부으면 (if swell)
Full Conjugation Example: 낫다 (to be better/recover)
Informal Polite (-아/어요)
Present:
- 나아요 (is better / recovering)
- 낫 + 아요 → 나아요 (ㅅ drops)
Past:
- 나았어요 (was better / recovered)
- 낫 + 았어요 → 나았어요 (ㅅ drops)
Future:
- 나을 거예요 (will be better / will recover)
- 낫 + 을 거예요 → 나을 거예요 (ㅅ drops)
Formal Polite (-습니다)
Present:
- 낫습니다 (is better / recovering)
- ㅅ kept before consonant
Past:
- 나았습니다 (was better / recovered)
- ㅅ drops before vowel
Future:
- 낫겠습니다 (will be better)
- ㅅ kept before consonant
Connective Forms
-지만 (but):
- 낫지만 (although better) - ㅅ kept
-아/어서 (so, because):
- 나아서 (because better)
- ㅅ drops before vowel
-고 (and):
- 낫고 (is better and) - ㅅ kept
Modifiers
-(으)ㄴ (descriptive):
- 나은 상태 (better condition)
- ㅅ drops
-(으)ㄹ (prospective):
- 나을 가능성 (possibility of becoming better)
- ㅅ drops
Full Conjugation Example: 짓다 (to build)
Informal Polite
Present:
- 지어요 (build)
- 짓 + 어요 → 지어요
Past:
- 지었어요 (built)
- 짓 + 었어요 → 지었어요
Future:
- 지을 거예요 (will build)
- 짓 + 을 거예요 → 지을 거예요
Formal Polite
Present:
- 짓습니다 (build)
- ㅅ kept
Past:
- 지었습니다 (built)
- ㅅ drops
Future:
- 짓겠습니다 (will build)
- ㅅ kept
Other Forms
-고 싶다:
- 짓고 싶어요 (want to build) - ㅅ kept
-지 않다:
- 짓지 않아요 (don't build) - ㅅ kept
-(으)면:
- 지으면 (if build) - ㅅ drops
Full Conjugation Example: 붓다 (to swell/to pour)
Note: 붓다 has two meanings with different conjugations:
붓다 (to swell) - ㅅ irregular
Present:
- 부어요 (swells)
- 붓 + 어요 → 부어요
Past:
- 부었어요 (swelled)
Modifier:
- 부은 얼굴 (swollen face)
붓다 (to pour) - Regular
Present:
- 부어요 (pour)
- Regular conjugation happens to look the same
The conjugation appears identical, but one is irregular and one is regular.
Common Expressions
낫다 (to be better/recover)
- 나아요 (is better / recovering)
- 나았어요 (got better / recovered)
- 감기가 나았어요 (The cold got better)
- 나은 것 같아요 (It seems better)
짓다 (to build)
- 집을 지어요 (build a house)
- 건물을 지었어요 (built a building)
- 지은 지 오래됐어요 (It's been long since it was built)
짓다 (to make - expressions/actions)
- 미소를 지어요 (make a smile)
- 표정을 지었어요 (made an expression)
- 농사를 지어요 (farm / cultivate crops)
붓다 (to swell)
- 발이 부어요 (The foot is swollen)
- 얼굴이 부었어요 (The face swelled)
- 부은 눈 (swollen eyes)
긋다 (to draw a line)
- 선을 그어요 (draw a line)
- 줄을 그었어요 (drew a line)
With Different Endings
-(으)ㄹ 거예요 (future)
ㅅ drops before ㄹ:
- 낫다 → 나을 거예요 (will be better)
- 짓다 → 지을 거예요 (will build)
- 붓다 → 부을 거예요 (will swell)
-(으)면 (if/when)
ㅅ drops before vowel:
- 낫다 → 나으면 (if better)
- 짓다 → 지으면 (if build)
- 붓다 → 부으면 (if swell)
-지 않다 (negative)
ㅅ kept before 지:
- 낫다 → 낫지 않아요 (not better)
- 짓다 → 짓지 않아요 (don't build)
- 붓다 → 붓지 않아요 (doesn't swell)
-고 싶다 (want to)
ㅅ kept before 고:
- 짓다 → 짓고 싶어요 (want to build)
-아/어서 (because)
ㅅ drops before vowel:
- 낫다 → 나아서 (because better)
- 짓다 → 지어서 (because build)
- 붓다 → 부어서 (because swell)
-고 (and)
ㅅ kept before 고:
- 낫다 → 낫고 (is better and)
- 짓다 → 짓고 (build and)
In Modifiers
Descriptive -(으)ㄴ:
- 낫다 → 나은 (better)
- 짓다 → 지은 (built)
- 붓다 → 부은 (swollen)
Prospective -(으)ㄹ:
- 낫다 → 나을 (will be better)
- 짓다 → 지을 (will build)
- 붓다 → 부을 (will swell)
Examples:
- 나은 상태 (better condition)
- 지은 지 3년 됐어요 (It's been 3 years since built)
- 부은 발목 (swollen ankle)
Identifying ㅅ Irregular Verbs
Check if stem ends in ㅅ:
- 낫다 → stem: 낫 (ends in ㅅ) ✓
- 짓다 → stem: 짓 (ends in ㅅ) ✓
Very few ㅅ irregular verbs exist.
Exceptions: Regular ㅅ Verbs
Most verbs ending in ㅅ are actually regular:
- 웃다 (utda) - to laugh → 웃어요 (not 우어요) - Regular!
- 씻다 (ssitda) - to wash → 씻어요 (not 씨어요) - Regular!
- 벗다 (beotda) - to take off → 벗어요 (not 버어요) - Regular!
Test: If ㅅ drops in conjugation (나아요, 지어요), it's irregular. If ㅅ stays (웃어요, 씻어요), it's regular.
짓다 Special Uses
짓다 has multiple meanings:
-
To build (structures):
- 집을 짓다 (build a house)
-
To make/form (expressions):
- 미소를 짓다 (make a smile)
- 표정을 짓다 (make an expression)
-
To cultivate (farming):
- 농사를 짓다 (farm)
- 벼를 짓다 (cultivate rice)
All follow the same ㅅ irregular conjugation.
Common Patterns in Sentences
Recovery:
- 감기가 나았어요. (The cold got better.)
- 아직 낫지 않았어요. (Haven't recovered yet.)
Building:
- 새 건물을 지어요. (They're building a new building.)
- 작년에 지었어요. (It was built last year.)
Swelling:
- 다리가 부었어요. (My leg is swollen.)
- 왜 부었어요? (Why is it swollen?)
Drawing lines:
- 선을 그으세요. (Please draw a line.)
Summary of Changes
Before vowel endings (-어/아, -으면, -을):
- ㅅ drops completely
- 낫다 → 나아요, 나으면, 나을
- 짓다 → 지어요, 지으면, 지을
Before consonant endings (-습니다, -지, -고, -겠):
- ㅅ stays
- 낫다 → 낫습니다, 낫지, 낫고
- 짓다 → 짓습니다, 짓지, 짓고
Key Points
- ✅ ㅅ drops completely before vowel endings
- ✅ ㅅ stays before consonant endings
- ✅ Very few ㅅ irregular verbs exist
- ✅ Common ones: 낫다, 짓다, 붓다 (swell), 긋다
- ✅ Most ㅅ verbs are regular: 웃다, 씻다, 벗다
- ✅ Test method: look for ㅅ disappearing in conjugation
Understanding ㅅ irregular verbs is simpler than other irregulars because there are so few of them, but they include some commonly used words for recovery and building.