The ㅂ irregular is the class you will use most, because it swallows almost every adjective you need to talk about the weather, food, and how things feel: 춥다 (cold), 덥다 (hot), 맵다 (spicy), 쉽다 (easy), 어렵다 (hard), 무겁다 (heavy). Learn this one pattern well and you can describe most of daily life. The rule is a single, clean sound change — stem-final ㅂ softens to 우, which then fuses with the ending — and this page also nails down the one point that trips everyone: which vowel the ending takes.
The mechanics: ㅂ → 우, then fuse
Take 덥다 ("is hot"). The stem is 덥-. Before a vowel-initial or 으-initial ending, the final ㅂ turns into 우, and that 우 merges with the ending's vowel:
- 덥- + -어요 → 더 + 우
- 어요 → 우 + 어 fuses to 워 → 더워요
- 덥- + -(으)면 → 더 + 우
- 면 → 더우면
- 덥- + -(으)ㄴ 날 → 더 + 우
- ㄴ → 더운 날 (a hot day)
That's the whole class. The ㅂ never simply liaises the way a regular batchim would — it becomes a vowel and dissolves into the ending.
오늘 날씨가 너무 추워요.
oneul nalssiga neomu chuwoyo
The weather is so cold today. (춥다 → 추워요)
이 김치 좀 매워요?
i gimchi jom maewoyo
Is this kimchi a bit spicy? (맵다 → 매워요)
한국어 발음이 생각보다 어려워요.
hangugeo bareumi saenggakboda eoryeowoyo
Korean pronunciation is harder than you'd think. (어렵다 → 어려워요)
Before consonant endings: nothing happens
Like every irregular, the ㅂ class is asleep before consonant-initial endings (-고, -지, -다, -네). The ㅂ stays put and the ending clamps straight on.
가방이 너무 무겁고 커요.
gabang-i neomu mugeopgo keoyo
The bag is really heavy and big. (무겁다 + -고 → 무겁고, ㅂ untouched)
So a single verb shows both faces: 무겁다 is 무겁고 before -고 but 무거워요 before -어요. If this "when does it fire?" split still feels shaky, review the three ending environments — the ㅂ class fires in environments 2 and 3 and rests in environment 1.
가방이 너무 무거워요.
gabang-i neomu mugeowoyo
The bag is too heavy. (무겁다 → 무거워요, before -어요)
The point everyone gets wrong: it's always 워, never 와
Here is the single most important fact about this class, and the one your instincts will fight. Normally, vowel harmony says a bright stem (last vowel ㅏ or ㅗ) takes 아, and 우/오 + 아 would give 와. So learners reason: 가깝다 has a bright ㅏ, therefore it should be ×가까와요. It doesn't.
The reason is that the ㅂ has already turned into 우, and once 우 is sitting there, it controls the fusion, not the original stem vowel. The inserted 우 always combines with 어 — never 아 — so the result is invariably 워:
우리 집은 학교에서 가까워요.
uri jibeun hakgyo-eseo gakkawoyo
My place is close to school. (가깝다, bright ㅏ, still → 가까워요, not ×가까와요)
가깝다's stem vowel is ㅏ, as bright as it gets, yet the form is 가까워요. The harmony rule you learned for regular verbs is genuinely overridden here. This is why you can safely stop worrying about 아 vs 어 for the entire ㅂ class: it is always 어 → 워.
The membership: mostly adjectives, one everyday verb
Almost all ㅂ-irregulars are descriptive verbs (adjectives) — a reminder that in Korean adjectives conjugate exactly like verbs. The high-frequency members:
| Dictionary | Meaning | 아/어-form | 으-form (-(으)면) |
|---|---|---|---|
| 춥다 | cold (weather) | 추워요 | 추우면 |
| 덥다 | hot (weather) | 더워요 | 더우면 |
| 맵다 | spicy | 매워요 | 매우면 |
| 쉽다 | easy | 쉬워요 | 쉬우면 |
| 어렵다 | difficult | 어려워요 | 어려우면 |
| 무겁다 | heavy | 무거워요 | 무거우면 |
| 가깝다 | near | 가까워요 | 가까우면 |
| 굽다 | grill/roast (verb) | 구워요 | 구우면 |
굽다 ("grill") is the one common verb in the club, and it behaves identically:
저는 생선을 자주 구워 먹어요.
jeoneun saengseoneul jaju guwo meogeoyo
I often grill fish and eat it. (굽다 → 구워)
The attributive and 으-forms in use
Because the ㅂ class fires before 으-endings too, you meet 더운/추운 (attributive), 더우면/추우면 (conditional), and 더우니까/추우니까 (causal) constantly:
이렇게 추운 날에는 집에 있고 싶어요.
ireoke chu-un nareneun jibe itgo sipeoyo
On a cold day like this, I want to stay home. (춥다 → 추운, attributive)
날씨가 추우면 감기에 걸리기 쉬워요.
nalssiga chu-umyeon gamgie geolligi swiwoyo
If it's cold, it's easy to catch a cold. (추우면 + 쉬워요)
너무 더워서 에어컨을 켰어요.
neomu deowoseo e-eokeoneul kyeosseoyo
It was so hot I turned on the AC. (덥다 → 더워서)
Bonus: the -스럽다 / -답다 / -롭다 suffixes are all ㅂ-irregular
A large productive family of adjectives is built with the suffixes -스럽다 ("-ish/-like"), -답다 ("worthy of / true to"), and -롭다 ("-ous"). All of them inherit the ㅂ-irregular pattern, so 사랑스럽다 → 사랑스러워요, 자유롭다 → 자유로워요, 학생답다 → 학생다워요:
강아지가 정말 사랑스러워요.
gang-ajiga jeongmal sarangseureowoyo
The puppy is so adorable. (-스럽다 → -스러워요)
Knowing that these suffixes are ㅂ-irregular means you can conjugate hundreds of derived adjectives without ever memorizing them one by one — one more payoff of reading the final jamo.
Common Mistakes
1. Keeping the ㅂ and just adding the ending. The ㅂ must soften to 우; it does not survive.
❌ 오늘은 정말 덥어요.
Wrong — stem-final ㅂ becomes 우 and fuses → 더워요, not ×덥어요.
✅ 오늘은 정말 더워요.
oneureun jeongmal deowoyo
It's really hot today.
2. Liaising the ㅂ like a regular batchim. ㅂ → 우, not ㅂ carried onto the next syllable.
❌ 오늘은 정말 더버요.
Wrong — the ㅂ turns into 우; it doesn't liaise as [버] → 더워요.
✅ 오늘은 정말 더워요.
oneureun jeongmal deowoyo
It's really hot today.
3. Harmonizing a bright stem to 와. The inserted 우 forces 워, even after a bright vowel.
❌ 우리 집은 학교에서 가까와요.
Wrong — ㅂ-irregulars are always 워, never 와, regardless of the stem vowel → 가까워요.
✅ 우리 집은 학교에서 가까워요.
uri jibeun hakgyo-eseo gakkawoyo
My place is close to school.
4. Forgetting the ㅂ softens before 으-endings too. 더우면, not ×덥으면.
❌ 내일 날씨가 덥으면 안 갈래요.
Wrong — the ㅂ softens before -(으)면 as well → 더우면.
✅ 내일 날씨가 더우면 안 갈래요.
naeil nalssiga deo-umyeon an gallaeyo
If it's hot tomorrow, I'd rather not go.
Key Takeaways
- ㅂ → 우, which fuses with the ending: 덥- + -어요 → 더워요; 덥- + -(으)면 → 더우면; 덥- + -(으)ㄴ → 더운.
- The ending vowel is always 어 → 워, never 와 — even after a bright-vowel stem (가까워요, not ×가까와요).
- Before consonant endings the ㅂ stays (덥고, 무겁지); it fires only before vowel and 으 endings.
- The class is mostly adjectives (춥다, 맵다, 쉽다, 어렵다) plus the verb 굽다, and includes all -스럽다/-답다/-롭다 adjectives.
- The only members that break the 우 pattern are 돕다 and 곱다 (→ 와) — see the exceptions page.
Now practice Korean
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Start learning Korean→Related Topics
- ㅂ Exceptions (돕다·곱다 → 도와/고와) and Regular ㅂ VerbsTOPIK 2 — The only two ㅂ-irregulars that go to 와 instead of 워 — 돕다 and 곱다 — plus the crucial boundary between irregular and regular ㅂ stems, which you cannot read off the spelling.
- When Irregulars Fire: The Three Ending EnvironmentsTOPIK 1 — Irregular stems only change before certain endings. Sort every ending into three environments — consonant-initial (safe, no change), 으-initial, and 아/어 vowel-initial (the strongest trigger) — and you can predict every irregular form.
- 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.
- Regular vs Irregular Predicates: The Big PictureTOPIK 1 — The seven irregular predicate classes are not chaos — each is a small, predictable sound change keyed to the stem's FINAL letter, and adjectives conjugate by the exact same machinery as verbs.
- Korean Adjectives Are Verbs (형용사 = Descriptive Verbs)TOPIK 1 — The one reframing that unlocks the whole group: a Korean 형용사 is a descriptive (stative) verb that conjugates like an action verb and predicates on its own — 좋다 already means 'to be good', so 날씨가 좋다 is a complete sentence with no copula and no separate 'to be'.