This is the page to bookmark. Once you understand the logic from the overview and the timing from the three ending environments, what you need day to day is a compact lookup: for a given class, what changes, when, and how do I tell it apart from a regular verb that happens to end in the same letter? Everything below fits on one screen, and every class page in this section links back here.
How to read the table
Each row gives you five things:
- Trigger — which ending environment wakes the change (all classes are safe before consonant endings like -고, -지).
- Change — what the stem-final jamo becomes.
- 아/어-form — the surface form before -아/어요 (present tense).
- 으-form — the surface form before an 으-ending like -(으)면 or -(으)세요.
- Regular look-alike — a common verb that ends in the same letter but does not belong to the class, so you don't over-apply the rule.
| Class | Model (meaning) | Change | 아/어-form | 으-form | Regular look-alike |
|---|---|---|---|---|---|
| ㅂ | 덥다 (hot) | ㅂ → 우 | 더워요 | 더우면 | 좁다 → 좁아요 |
| ㄷ | 듣다 (hear) | ㄷ → ㄹ | 들어요 | 들으면 | 닫다 → 닫아요 |
| ㅅ | 짓다 (build) | ㅅ drops, no contraction | 지어요 | 지으면 | 웃다 → 웃어요 |
| 르 | 모르다 (not know) | 르 → ㄹㄹ | 몰라요 | — (르 is a vowel ending) | 따르다 → 따라요 |
| 으 | 쓰다 (write) | ㅡ drops | 써요 | — (으 already vowel-final) | (the "regular" default itself) |
| ㄹ | 살다 (live) | ㄹ drops before ㄴ/ㅂ/ㅅ/오 | 살아요 | 사세요 · 삽니다 · 사는 | (few true regular ㄹ-final stems) |
| ㅎ | 그렇다 (be so) | ㅎ drops, vowel → ㅐ | 그래요 | 그러면 · 그런 | 좋다 → 좋아요 |
| 러 | 이르다 (reach) | ending 어 → 러 | 이르러요 | 이르면 | (only ~4 members) |
Two of these rows do most of the damage in real learning, so let's zoom in on the two contrasts that decide almost every hard case.
Contrast 1: is a ㄷ / ㅂ / ㅅ stem irregular or regular?
This is a vocabulary fact you attach to each word — you cannot read it off the spelling. 듣다 and 닫다 both end in ㄷ; one is irregular, one is regular, and they look identical. The same is true of 춥다 vs 좁다 (both ㅂ) and 짓다 vs 웃다 (both ㅅ). The change surfaces only before a vowel or 으, so that is exactly where the two split:
뉴스 들으면 한국어 실력이 늘어요.
nyuseu deureumyeon hangugeo sillyeogi neureoyo
Your Korean improves if you listen to the news. (듣다 IRREGULAR → 들으면)
문 좀 닫아 주세요.
mun jom dada juseyo
Please close the door. (닫다 REGULAR → 닫아, ㄷ just liaises)
The everyday members you simply have to know:
- ㄷ-irregular: 듣다 (hear), 걷다 (walk), 묻다 (ask), 싣다 (load). Regular: 닫다 (close), 받다 (receive), 믿다 (believe), 얻다 (obtain).
- ㅂ-irregular: most adjectives — 춥다, 덥다, 맵다, 쉽다, 어렵다 — plus verb 굽다. Regular: 좁다, 입다, 잡다, 씹다.
- ㅅ-irregular: 짓다 (build), 낫다 (heal/better), 붓다 (pour/swell), 젓다 (stir). Regular: 웃다 (laugh), 씻다 (wash), 벗다 (take off).
저는 강릉에 삽니다.
jeoneun gangneung-e samnida
I live in Gangneung. (formal — 살다 → 삽니다, ㄹ drops, ㅂ nasalizes to ㅁ)
밥은 제가 지을게요.
babeun jega ji-eulgeyo
I'll cook the rice. (짓다 → 지을게요, ㅅ drops before the 으-ending)
Contrast 2: true 르-irregular vs 으-drop imposter
Every stem ending in 르 looks like it should double its ㄹ, but a good many are secretly plain 으-drop stems that just happen to have ㄹ before the ㅡ. The two produce completely different forms, and only one has the doubled ㄹ:
- True 르-irregular doubles the ㄹ: 모르다 → 몰라요, 부르다 → 불러요, 빠르다 → 빨라요, 다르다 → 달라요.
- 으-drop imposter just drops the ㅡ: 따르다 → 따라요, 치르다 → 치러요, 들르다 → 들러요.
저는 그 사람 이름을 몰라요.
jeoneun geu saram ireumeul mollayo
I don't know that person's name. (모르다 → 몰라요, doubled ㄹ)
아이가 엄마를 잘 따라요.
aiga eommareul jal ttarayo
The child is really attached to mom. (따르다 → 따라요, plain 으-drop, NO doubling)
There is no spelling cue that separates them — 모르다 and 따르다 are identical in shape — so this too is a per-word fact. The good news is that the true 르-irregulars are far more numerous, and the imposters are a short list (따르다, 치르다, 들르다, 다다르다). The full treatment is on 르-irregular vs 으-drop.
The everyday 으 and ㄹ classes
The 으-drop class is the most predictable of all — a stem-final ㅡ simply vanishes before -아/어, with no exceptions worth worrying about:
요즘 소설을 써요.
yojeum soseoreul sseoyo
I'm writing a novel these days. (쓰다 → 써요)
키가 정말 커요.
kiga jeongmal keoyo
You're really tall. (크다 → 커요)
The ㄹ-drop class is unusual because it fires before certain consonant endings (those starting with ㄴ, ㅂ, ㅅ, and the honorific 오/시), not before vowels — the mirror image of every other class. Before -아/어 it does nothing (살아요, not a special form), but before -ㅂ니다, -네, -세요, and -는 the ㄹ disappears. Its two behaviors get separate pages: the ㄹ-drop rules and its role in the attributive.
Recognizing the two rare classes
The ㅎ-irregular covers nearly all color and "such/that kind" adjectives (빨갛다, 노랗다, 파랗다, 그렇다, 어떻다) — the ㅎ drops and the leftover vowel fuses to ㅐ, giving 그래요, 어때요, 빨개요. And the 러-irregular is a four-word museum piece (이르다 "reach," 푸르다 "be blue," 누르다 "be yellow," 노르다 "be golden") where the ending's 어 becomes 러: 이르러요, 푸르러요. Recognize them; you'll rarely produce them.
Common Mistakes
1. Over-generalizing the ㄷ-irregular to a regular ㄷ verb. 받다 ends in ㄷ but is regular.
❌ 선물을 바라요.
Wrong — 받다 is regular, not like 듣다. The ㄷ just liaises → 받아요.
✅ 선물을 받아요.
seonmureul badayo
I receive a gift.
2. Treating a 으-drop imposter as a 르-irregular. 따르다 does not double its ㄹ.
❌ 아이가 엄마를 딸라요.
Wrong — 따르다 is a plain 으-drop stem; no doubling → 따라요.
✅ 아이가 엄마를 따라요.
aiga eommareul ttarayo
The child follows mom around.
3. Making a regular ㅅ verb drop its ㅅ. 웃다 keeps its ㅅ, which liaises normally.
❌ 아기가 우어요.
Wrong — 웃다 is regular; the ㅅ liaises, it doesn't drop → 웃어요.
✅ 아기가 웃어요.
agiga useoyo
The baby is smiling.
4. Making a regular ㄷ verb turn ㄷ into ㄹ. 닫다 keeps its ㄷ.
❌ 창문을 다라요.
Wrong — 닫다 is regular; the ㄷ liaises → 닫아요.
✅ 창문을 닫아요.
changmuneul dadayo
I'm closing the window.
Key Takeaways
- This table is the hub: class, trigger, change, 아/어-form, 으-form, and a regular look-alike for each.
- Contrast 1 — whether a ㄷ/ㅂ/ㅅ stem is irregular or regular is a per-word fact; spelling won't tell you (듣다 vs 닫다).
- Contrast 2 — a 르-stem is truly irregular only if its form has a doubled ㄹ (몰라요); imposters just drop ㅡ (따라요).
- Don't over-generalize a class to every stem that ends in that letter — 받다, 웃다, 닫다 are regular.
- The 으-drop class is the most predictable; the ㄹ-drop class uniquely fires before consonant endings.
Now practice Korean
Reading grammar gets you part of the way. The exercises are where it sticks — free, no signup needed.
Start learning Korean→Related Topics
- 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.
- 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.
- 르-Irregular vs 으-Drop Imposters (따르다 → 따라요)TOPIK 2 — Three stems that END in 르 — 따르다, 치르다, 들르다 — are NOT 르-irregular but plain 으-drop verbs, so they take a single ㄹ (따라요), never the doubled ㄹ of a true 르-irregular (달라요). One letter apart, opposite outputs.
- The ㅂ Irregular: 덥다 → 더워요TOPIK 1 — How stem-final ㅂ softens to 우 and fuses with the ending — the class that covers almost every weather and sensation adjective — plus the rule that the ending vowel here is ALWAYS 어 → 워, never 와.
- ㄷ Homograph Traps and Regular ㄷ VerbsTOPIK 2 — Why 걷다 and 묻다 each split into an irregular and a regular verb by meaning, and the common ㄷ verbs (받다, 닫다, 믿다…) that keep their ㄷ before every ending.