Korean irregular verbs frustrate learners because they arrive without warning. You learn 덥다 means "hot," then hear 더워요 and wonder where the ㅂ went.
The good news: there are seven patterns, they are triggered by the final letter of the stem, and once you know the trigger you can predict most of them.
The bad news: for each pattern, some verbs are regular anyway, and you have to learn which.
1. ㅂ irregular
ㅂ becomes 우 before a vowel ending.
| Verb | Conjugated |
|---|---|
| 덥다 (hot) | 더워요 |
| 춥다 (cold) | 추워요 |
| 쉽다 (easy) | 쉬워요 |
| 어렵다 (difficult) | 어려워요 |
| 맵다 (spicy) | 매워요 |
Regular ones: 입다 → 입어요, 좁다 → 좁아요, 잡다 → 잡아요
Rule of thumb: most adjectives ending in ㅂ are irregular; most verbs are regular.
Special case: 돕다 (to help) → 도와요, not 도워요.
2. ㄷ irregular
ㄷ becomes ㄹ before a vowel ending.
| Verb | Conjugated |
|---|---|
| 듣다 (listen) | 들어요 |
| 걷다 (walk) | 걸어요 |
| 묻다 (ask) | 물어요 |
Regular ones: 받다 → 받아요, 닫다 → 닫아요, 믿다 → 믿어요
듣다 and 걷다 are common enough that most learners meet the irregular before the regular.
3. 르 irregular
Stems ending in 르 double the ㄹ and drop the 으.
| Verb | Conjugated |
|---|---|
| 모르다 (not know) | 몰라요 |
| 다르다 (different) | 달라요 |
| 빠르다 (fast) | 빨라요 |
| 부르다 (call, sing) | 불러요 |
This one is fully consistent — nearly every 르 verb behaves this way, so once you spot 르 at the end of a stem you can predict the form.
몰라요 is among the most useful words in the language, so this pattern arrives early.
4. 으 drop
A final 으 disappears before a vowel ending, and the vowel before it decides 아 or 어.
| Verb | Conjugated |
|---|---|
| 쓰다 (write, use) | 써요 |
| 크다 (big) | 커요 |
| 바쁘다 (busy) | 바빠요 |
| 예쁘다 (pretty) | 예뻐요 |
| 아프다 (hurt) | 아파요 |
바쁘다 has ㅏ before the 으, so it takes 아 → 바빠요. 예쁘다 has ㅖ, so it takes 어 → 예뻐요.
This one is completely regular within itself, with no exceptions to memorise.
5. ㅅ irregular
ㅅ disappears before a vowel ending, leaving the vowels side by side.
| Verb | Conjugated |
|---|---|
| 짓다 (build) | 지어요 |
| 낫다 (get better) | 나아요 |
| 붓다 (pour, swell) | 부어요 |
Regular ones: 웃다 → 웃어요, 씻다 → 씻어요, 벗다 → 벗어요
Note that the vowels do not contract here — 지어요 stays two syllables.
6. ㅎ irregular
Mostly colour adjectives and the 그렇다 family. ㅎ drops and the vowel changes to ㅐ.
| Verb | Conjugated |
|---|---|
| 그렇다 (be so) | 그래요 |
| 어떻다 (be how) | 어때요 |
| 빨갛다 (red) | 빨개요 |
| 하얗다 (white) | 하얘요 |
Regular one: 좋다 → 좋아요 — the most common ㅎ adjective of all, and it is regular.
어때요 is worth noting: it is the ㅎ irregular form of 어떻다, and you use it constantly. 이거 어때요?
7. ㄹ drop
ㄹ disappears before ㄴ, ㅂ, ㅅ — but not before vowels.
| Verb | Form |
|---|---|
| 살다 (live) | 살아요 / 삽니다 / 사세요 / 사는 |
| 알다 (know) | 알아요 / 압니다 / 아세요 / 아는 |
| 만들다 (make) | 만들어요 / 만듭니다 / 만드세요 |
So the 요 form looks normal and the formal and honorific forms lose the ㄹ. This is the pattern most likely to surprise you later rather than immediately.
How to actually learn these
Do not study all seven at once. They arrive at very different frequencies.
덥다, 춥다, 듣다, 모르다, 바쁘다, 어때요 appear constantly, and learning those six words individually teaches you five of the seven patterns without any conscious rule study.
The rules become useful later, as confirmation of something you already half know.
K-PATTO dialogue is where these show up in their natural frequency rather than in a table — you meet 몰라요 and 어때요 many times before you ever meet 붓다. The first ten episodes are free at K-PATTO.