으 Irregular Verbs (으 불규칙)

으 irregular verbs (으 불규칙) are verbs and adjectives whose stem ends with the vowel 으 and drop this vowel when followed by endings that start with a vowel.

What Makes Them Irregular

Regular verbs maintain their stem throughout conjugation. 으 irregular verbs drop the 으 vowel from their stem before vowel-starting endings.

Rule

When stem ending in 으 meets vowel-starting endings:

• The 으 drops before vowel endings (-아/어, -으면)
• The stem combines directly with the ending
• 으 is kept before consonant-starting endings

Vowel harmony after dropping 으:

• If the remaining syllable has ㅏ or ㅗ → use -아
• Otherwise → use -어

Common 으 Irregular Verbs

Many common verbs and adjectives follow this pattern:

• 쓰다 (sseuda) - to write, to use, to be bitter
• 끄다 (kkeuda) - to turn off, to extinguish
• 크다 (keuda) - to be big
• 예쁘다 (yeppeuda) - to be pretty
• 아프다 (apeuda) - to be sick/hurt
• 바쁘다 (bappeuda) - to be busy
• 기쁘다 (gippeuda) - to be happy/glad
• 슬프다 (seulpeuda) - to be sad
• 나쁘다 (nappeuda) - to be bad

Conjugation Pattern

Pattern 1: 으 Drops Before -어/아

쓰다 (to write):

• 쓰 → 스 (으 drops) + 어요 → 써요
  • 스 + 어 contracts to 써

끄다 (to turn off):

• 끄 → 끄 (으 drops) + 어요 → 꺼요
  • ㄲ + 어 = 꺼

크다 (to be big):

• 크 → 크 (으 drops) + 어요 → 커요
  • Vowel is ㅡ (neutral) → uses 어

예쁘다 (to be pretty):

• 예쁘 → 예쁘 (으 drops) + 어요 → 예뻐요

아프다 (to hurt):

• 아프 → 아프 (으 drops) + 어요 → 아파요
  • After dropping 으, stem has ㅏ → uses 아

Pattern 2: 으 Kept Before Consonants

Before -습니다:

• 쓰다 → 씁니다 (write - formal)
• 크다 → 큽니다 (is big - formal)
• 예쁘다 → 예쁩니다 (is pretty - formal)

Before -지:

• 쓰다 → 쓰지 않아요 (don't write)
• 크다 → 크지 않아요 (not big)

Before -고:

• 쓰다 → 쓰고 (write and)
• 크다 → 크고 (is big and)

Full Conjugation Example: 쓰다 (to write)

Informal Polite (-아/어요)

Present:

• 써요 (write)
  • 쓰 → 스 + 어요 → 써요

Past:

• 썼어요 (wrote)
  • 쓰 → 스 + 었어요 → 썼어요

Future:

• 쓸 거예요 (will write)
  • 쓰 + ㄹ 거예요 → 쓸 거예요

Formal Polite (-습니다)

Present:

• 씁니다 (write)
  • 으 kept before consonant

Past:

• 썼습니다 (wrote)
  • 으 drops before vowel

Future:

• 쓰겠습니다 (will write)
  • 으 kept before consonant

Connective Forms

-지만 (but):

• 쓰지만 (although write) - 으 kept

-아/어서 (so, because):

• 써서 (because write)
  • 으 drops before vowel

-고 (and):

• 쓰고 (write and) - 으 kept

Modifiers

-(으)ㄴ (descriptive):

• 쓴 (written)
  • 으 drops, just add ㄴ

-(으)ㄹ (prospective):

• 쓸 (will write)
  • 으 drops, just add ㄹ

Full Conjugation Example: 크다 (to be big)

Informal Polite

Present:

• 커요 (is big)
  • 크 + 어요 → 커요

Past:

• 컸어요 (was big)
  • 크 + 었어요 → 컸어요

Future:

• 클 거예요 (will be big)
  • 크 + ㄹ 거예요 → 클 거예요

Formal Polite

Present:

• 큽니다 (is big)
  • 으 kept

Past:

• 컸습니다 (was big)
  • 으 drops

Future:

• 크겠습니다 (will be big)
  • 으 kept

Modifiers

-(으)ㄴ:

• 큰 (big)
  • 크 + ㄴ → 큰

-(으)ㄹ:

• 클 (will be big)
  • 크 + ㄹ → 클

Examples:

• 큰 집 (big house)
• 클 가능성 (possibility of being big)

Full Conjugation Example: 예쁘다 (to be pretty)

Informal Polite

Present:

• 예뻐요 (is pretty)
  • 예쁘 → 예쁘 + 어요 → 예뻐요

Past:

• 예뻤어요 (was pretty)
  • 예쁘 + 었어요 → 예뻤어요

Future:

• 예쁠 거예요 (will be pretty)
  • 예쁘 + ㄹ 거예요 → 예쁠 거예요

Formal Polite

Present:

• 예쁩니다 (is pretty)
  • 으 kept

Past:

• 예뻤습니다 (was pretty)

Future:

• 예쁘겠습니다 (will be pretty)

Modifiers

-(으)ㄴ:

• 예쁜 (pretty)
  • 예쁘 + ㄴ → 예쁜

Example:

• 예쁜 꽃 (pretty flower)

Full Conjugation Example: 아프다 (to hurt/be sick)

Informal Polite

Present:

• 아파요 (hurts / is sick)
  • 아프 → 아프 + 어요 → 아파요 (uses 아 because of ㅏ)

Past:

• 아팠어요 (hurt / was sick)
  • 아프 + 었어요 → 아팠어요

Future:

• 아플 거예요 (will hurt / will be sick)
  • 아프 + ㄹ 거예요 → 아플 거예요

Formal Polite

Present:

• 아픕니다 (hurts / is sick)

Past:

• 아팠습니다 (hurt / was sick)

Future:

• 아프겠습니다 (will hurt)

Modifiers

-(으)ㄴ:

• 아픈 (sick/hurting)
  • 아프 + ㄴ → 아픈

Examples:

• 아픈 사람 (sick person)
• 머리가 아파요 (My head hurts)

Vowel Harmony After Dropping 으

After dropping 으, check the remaining syllable's vowel:

Use -아 if stem has ㅏ or ㅗ:

• 아프다 → 아프 → 아파요 (has ㅏ)
• 잠그다 → 잠그 → 잠가요 (has ㅏ)

Use -어 for all other vowels:

• 크다 → 크 → 커요 (neutral ㅡ)
• 쓰다 → 쓰 → 써요 (neutral ㅡ)
• 예쁘다 → 예쁘 → 예뻐요 (has ㅖ)
• 슬프다 → 슬프 → 슬퍼요 (has ㅡ)

Common Expressions

쓰다 (to write/use)

• 편지를 써요 (write a letter)
• 펜을 써요 (use a pen)
• 썼어요 (wrote / used)

끄다 (to turn off)

• 불을 꺼요 (turn off the light)
• 컴퓨터를 껐어요 (turned off the computer)

크다 (to be big)

• 집이 커요 (The house is big)
• 큰 나무 (big tree)
• 컸어요 (was big / grew big)

예쁘다 (to be pretty)

• 예뻐요 (is pretty)
• 예쁜 옷 (pretty clothes)
• 예뻤어요 (was pretty)

아프다 (to hurt/be sick)

• 배가 아파요 (My stomach hurts)
• 감기에 걸려서 아파요 (I'm sick with a cold)
• 아픈 것 같아요 (I think I'm sick)

바쁘다 (to be busy)

• 요즘 바빠요 (I'm busy these days)
• 바쁜 일상 (busy daily life)
• 너무 바빴어요 (was too busy)

기쁘다 (to be happy)

• 기뻐요 (is happy)
• 기쁜 소식 (happy news)
• 만나서 기뻤어요 (was happy to meet)

슬프다 (to be sad)

• 슬퍼요 (is sad)
• 슬픈 영화 (sad movie)
• 너무 슬펐어요 (was too sad)

나쁘다 (to be bad)

• 나빠요 (is bad)
• 나쁜 사람 (bad person)
• 나빴어요 (was bad)

With Different Endings

-(으)ㄹ 거예요 (future)

으 drops before ㄹ:

• 쓰다 → 쓸 거예요 (will write)
• 크다 → 클 거예요 (will be big)
• 예쁘다 → 예쁠 거예요 (will be pretty)

-(으)면 (if/when)

으 drops before 으:

• 쓰다 → 쓰면 (if write)
• 크다 → 크면 (if big)
• 아프다 → 아프면 (if sick)

-지 않다 (negative)

으 kept before 지:

• 쓰다 → 쓰지 않아요 (don't write)
• 크다 → 크지 않아요 (not big)
• 예쁘다 → 예쁘지 않아요 (not pretty)

-고 싶다 (want to)

으 kept before 고:

• 쓰다 → 쓰고 싶어요 (want to write)
• 끄다 → 끄고 싶어요 (want to turn off)

-아/어서 (because)

으 drops before vowel:

• 쓰다 → 써서 (because write)
• 커서 (because big)
• 아파서 (because sick)
• 예뻐서 (because pretty)

-고 (and)

으 kept before 고:

• 쓰다 → 쓰고 (write and)
• 크다 → 크고 (is big and)
• 예쁘다 → 예쁘고 (is pretty and)

In Modifiers

Descriptive -(으)ㄴ:

• 쓰다 → 쓴 (written / bitter)
• 크다 → 큰 (big)
• 예쁘다 → 예쁜 (pretty)
• 아프다 → 아픈 (sick)
• 바쁘다 → 바쁜 (busy)

Prospective -(으)ㄹ:

• 쓰다 → 쓸 (will write)
• 크다 → 클 (will be big)
• 예쁘다 → 예쁠 (will be pretty)

Examples:

• 큰 문제 (big problem)
• 예쁜 여자 (pretty woman)
• 아픈 다리 (hurt leg)
• 바쁜 하루 (busy day)

Identifying 으 Irregular Verbs

Check if stem ends in 으:

• 쓰다 → stem: 쓰 (ends in vowel 으) ✓
• 크다 → stem: 크 (ends in vowel 으) ✓
• 예쁘다 → stem: 예쁘 (ends in 으) ✓

Almost all verbs/adjectives with 으 final vowel are irregular.

Very Rare Exceptions

Nearly all 으-stem words are irregular. Regular 으 verbs are extremely rare in modern Korean.

Common Patterns in Sentences

Descriptions:

• 집이 커요. (The house is big.)
• 날씨가 좋고 예뻐요. (The weather is nice and pretty.)

Physical state:

• 머리가 아파요. (My head hurts.)
• 다리가 아팠어요. (My leg hurt.)

Busy:

• 요즘 너무 바빠요. (I'm too busy these days.)
• 바쁜 일이 많아요. (I have many busy things.)

Emotions:

• 기뻐요! (I'm happy!)
• 너무 슬펐어요. (I was so sad.)

Actions:

• 편지를 써요. (I write a letter.)
• 불을 꺼요. (I turn off the light.)

Summary of Changes

Before vowel endings (-어/아, -(으)ㄴ, -(으)ㄹ):

• 으 drops
• 쓰다 → 써요, 쓴, 쓸
• 크다 → 커요, 큰, 클
• 예쁘다 → 예뻐요, 예쁜, 예쁠

Before consonant endings (-습니다, -지, -고, -겠):

• 으 stays
• 쓰다 → 씁니다, 쓰지, 쓰고
• 크다 → 큽니다, 크지, 크고

Key Points

• ✅ 으 drops before vowel endings
• ✅ 으 stays before consonant endings
• ✅ Check vowel harmony after dropping 으
• ✅ Common verbs: 쓰다, 끄다, 크다, 예쁘다, 아프다
• ✅ Pattern: 쓰다→써요, 크다→커요, 아프다→아파요
• ✅ Nearly all 으-stem words are irregular

Understanding 으 irregular verbs is essential as they include many common adjectives for descriptions and states, as well as frequently used verbs.