The 르-irregular (르 불규칙) governs a cluster of the most common predicates in the language — 모르다 ("not know"), 다르다 ("be different"), 빠르다 ("be fast"), 부르다 ("call / sing / be full") — and produces the striking doubled-ㄹ shape you have surely already heard: 모르다 → 몰라요. The good news is that the trigger is narrow: only the 아/어 endings set it off. Before consonant endings and 으-endings the stem stays perfectly regular. This page is the paradigm grid, split into the doublers, the 으-drop imposters that only look like them, and the separate 러-irregular pair.
The one-line rule behind the grid
When an 아/어 ending attaches to a stem ending in 르, two things happen at once: (1) the 으 of 르 drops, and (2) an extra ㄹ appears as the batchim of the previous syllable — giving a doubled ㄹ. So 모르 + 아 → 몰 + 라 → 몰라, and 부르 + 어 → 불 + 러 → 불러. Whether you get 라 or 러 is ordinary vowel harmony on the syllable before 르: bright (ㅏ/ㅗ) → 라, otherwise → 러. The conceptual walkthrough lives on the 르 irregular explained page; this page is the table.
Full table: the doublers (르-irregular)
Columns: dictionary form, the everyday polite 해요체 (-아/어요), the sequential/causal -아서/어서, the past -았/었어요, and a consonant ending -(으)면 to show the stem going back to normal. Notice the whole 아/어 column and the -아서/어서 and past columns double the ㄹ, while the -(으)면 column does not.
| Dictionary (meaning) | 해요체 -아/어요 | -아서/어서 | Past -았/었어요 | Condition -(으)면 |
|---|---|---|---|---|
| 모르다 (not know) | 몰라요 mollayo | 몰라서 mollaseo | 몰랐어요 mollasseoyo | 모르면 moreumyeon |
| 다르다 (be different) | 달라요 dallayo | 달라서 dallaseo | 달랐어요 dallasseoyo | 다르면 dareumyeon |
| 빠르다 (be fast) | 빨라요 ppallayo | 빨라서 ppallaseo | 빨랐어요 ppallasseoyo | 빠르면 ppareumyeon |
| 자르다 (cut) | 잘라요 jallayo | 잘라서 jallaseo | 잘랐어요 jallasseoyo | 자르면 jareumyeon |
| 고르다 (choose) | 골라요 gollayo | 골라서 gollaseo | 골랐어요 gollasseoyo | 고르면 goreumyeon |
| 부르다 (call/sing/be full) | 불러요 bulleoyo | 불러서 bulleoseo | 불렀어요 bulleosseoyo | 부르면 bureumyeon |
| 흐르다 (flow) | 흘러요 heulleoyo | 흘러서 heulleoseo | 흘렀어요 heulleosseoyo | 흐르면 heureumyeon |
The harmony split is on display: 모르다, 빠르다, 다르다, 자르다, 고르다 all have a bright vowel (ㅗ or ㅏ) in the syllable before 르, so they take 라; 부르다 (ㅜ) and 흐르다 (ㅡ) are dark, so they take 러.
죄송한데 저도 그건 잘 몰라요.
joesonghande jeodo geugeon jal mollayo
Sorry, I don't really know that one either. (모르다 → 몰라요)
노래방에서 두 시간 동안 노래를 불렀어요.
noraebang-eseo du sigan dong-an noraereul bulleosseoyo
We sang for two hours straight at the noraebang. (부르다 → 불렀어요)
쌍둥이인데 성격이 너무 달라서 신기해요.
ssangdung-ininde seonggyeogi neomu dallaseo singihaeyo
They're twins, but their personalities are so different it's fascinating. (다르다 → 달라서)
어제 미용실에서 머리를 짧게 잘랐어요.
eoje miyongsireseo meorireul jjalge jallasseoyo
I got my hair cut short at the salon yesterday. (자르다 → 잘랐어요)
마음에 드는 걸로 하나 골라 보세요.
ma-eume deuneun geollo hana golla boseyo
Go ahead and pick one you like. (고르다 → 골라)
나이가 드니까 시간이 정말 빠르게 흘러요.
naiga deunikka sigani jeongmal ppareuge heulleoyo
As I get older, time really does fly by. (흐르다 → 흘러요)
Only 아/어 triggers it — the -(으)면 column proves it
The right-hand column of the table is doing important work: before a consonant ending or an 으-ending, a 르 stem is completely regular — no dropped 으, no doubled ㄹ. Because the stem 모르 already ends in a vowel, endings like -면 and -니까 attach straight on with no buffer.
길을 모르면 언제든지 저한테 전화하세요.
gireul moreumyeon eonjedeunji jeohante jeonhwahaseyo
If you don't know the way, call me anytime. (모르면 — no doubling before -면)
이건 제가 아는 노래랑 완전히 다른 곡이에요.
igeon jega aneun noraerang wanjeonhi dareun gogieyo
This is a totally different song from the one I know. (다르다 → 다른, no doubling before the modifier)
Imposters: 따르다 and 치르다 are 으-drop, not 르-irregular
A few common stems look like 르-irregulars but belong to the plain 으-drop class: they drop the 으 and take a single ㄹ, with no pushed-back batchim. The result is 따라요, not ×딸라요.
| Dictionary (meaning) | 해요체 -아/어요 | -아서/어서 | Past -았/었어요 | Condition -(으)면 |
|---|---|---|---|---|
| 따르다 (follow / pour) | 따라요 ttarayo | 따라서 ttaraseo | 따랐어요 ttarasseoyo | 따르면 ttareumyeon |
| 치르다 (pay / undergo) | 치러요 chireoyo | 치러서 chireoseo | 치렀어요 chireosseoyo | 치르면 chireumyeon |
(들르다, "drop by," is the same kind of imposter: 들러요, with the single ㄹ coming from the stem's own 들-.) There is no shortcut for telling doublers from imposters — it is lexical — so the 르 vs 으-drop page lays out the members side by side.
저는 보통 선배 의견을 따라요.
jeoneun botong seonbae uigyeoneul ttarayo
I usually go along with my senior's opinion. (따르다 → 따라요, single ㄹ)
지난주에 드디어 기말시험을 치렀어요.
jinanjue deudieo gimalsiheomeul chireosseoyo
I finally sat my final exams last week. (치르다 → 치렀어요, single ㄹ)
The other lookalike: the 러-irregular (이르다, 푸르다)
A tiny, separate class — the 러-irregular — also ends in 르 but neither doubles nor drops. Instead it adds 러 to the intact stem: 이르 + 어 → 이르러. The two everyday members are 이르다 ("arrive / reach," somewhat formal or literary) and 푸르다 ("be blue / verdant"). Before consonant and 으-endings they too are regular (이르면, 푸르면).
| Dictionary (meaning) | 해요체 -아/어요 | -아서/어서 | Past -았/었어요 | Condition -(으)면 |
|---|---|---|---|---|
| 이르다 (arrive/reach) | 이르러요 ireureoyo | 이르러서 ireureoseo | 이르렀어요 ireureosseoyo | 이르면 ireumyeon |
| 푸르다 (be blue/verdant) | 푸르러요 pureureoyo | 푸르러서 pureureoseo | 푸르렀어요 pureureosseoyo | 푸르면 pureumyeon |
가을이라 하늘이 정말 높고 푸르러요.
ga-eurira haneuri jeongmal nopgo pureureoyo
It's autumn, so the sky is really high and blue. (푸르다 → 푸르러요)
Why English speakers find the doubling so odd
English has no operation where a consonant copies itself backward onto the previous syllable. Its doubled letters (run → running, stop → stopped) are a spelling convention that keeps a vowel short — the extra letter is silent and changes nothing you say. The Korean 르-doubling is the opposite: it is a pronounced resyllabification, where a real ㄹ sound splits into a coda plus an onset (불러 = 불 + 러, two audible ㄹ's). The mental model that helps is not "add a letter" but "the ㄹ lands on both sides of the syllable break." Once 불러 and 몰라 stop looking like typos and start looking like 불·러 and 몰·라, the whole class becomes automatic.
Common Mistakes
1. Writing a single ㄹ instead of doubling. The signature error.
❌ 저는 그 답을 잘 모라요.
Wrong — the ㄹ doubles: 몰라요.
✅ 저는 그 답을 잘 몰라요.
jeoneun geu dabeul jal mollayo
I don't really know the answer.
2. Doubling before a non-아/어 ending. The doubling is triggered only by 아/어.
❌ 길을 몰라면 지도를 보세요.
Wrong — before -(으)면 the stem is regular: 모르면.
✅ 길을 모르면 지도를 보세요.
gireul moreumyeon jidoreul boseyo
If you don't know the way, look at a map.
3. Wrong 라/러 harmony. 부르다 is dark (ㅜ), so it takes 러.
❌ 많이 먹어서 배가 불라요.
Wrong — dark vowel ㅜ takes 러: 불러요.
✅ 많이 먹어서 배가 불러요.
mani meogeoseo baega bulleoyo
I ate so much that I'm full.
4. Doubling an imposter. 따르다 is a plain 으-drop verb.
❌ 저는 형을 잘 딸라요.
Wrong — 따르다 is 으-drop: 따라요 (single ㄹ).
✅ 저는 형을 잘 따라요.
jeoneun hyeong-eul jal ttarayo
I follow my older brother's lead closely.
5. Treating a 러-irregular as a doubler. 이르다 "arrive" adds 러; it does not double.
❌ 드디어 정상에 일러요.
Wrong for 'reach' — 이르다 is 러-irregular: 이르러요. (일러요 would be 이르다 'tell on / inform', a different verb.)
✅ 드디어 정상에 이르러요.
deudieo jeongsang-e ireureoyo
At last we reach the summit. (formal/literary)
Key Takeaways
- Before an 아/어 ending, a 르 stem drops the 으 and doubles the ㄹ: 모르다 → 몰라요, 부르다 → 불러요; the -아서/어서 and past forms double too (몰라서, 불렀어요).
- 라 vs 러 follows harmony on the syllable before 르: bright (ㅏ/ㅗ) → 라, otherwise → 러.
- Only 아/어 endings trigger it — before consonant or 으-endings the stem is regular (모르면, 다른, 부르니까).
- 따르다 → 따라요 and 치르다 → 치러요 are 으-drop imposters with a single ㄹ, not doublers.
- 이르다 → 이르러요 and 푸르다 → 푸르러요 are the separate 러-irregular, which adds 러 rather than doubling — see the master chart.
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Start learning Korean→Related Topics
- 으-Drop Verbs (으 탈락): Full TableTOPIK 1 — The complete lookup grid for the 으-drop pattern — any stem whose final vowel is ㅡ drops it before an 아/어 ending (쓰다 → 써요), with harmony set by the syllable one step back (바쁘다 → 바빠요, 예쁘다 → 예뻐요). The most systematic of all the 'irregular' classes, with zero lexical exceptions.
- Irregular vs Regular: The Look-Alike Master TableTOPIK 3 — The cheat-card for the question learners actually ask — 'this verb ends in ㄷ/ㅅ/ㅂ/ㅎ/르, does it inflect irregularly?' A single minimal-pair table sets each irregular next to a regular verb with the same final consonant, so you can see that irregularity is lexical, not spelling-based, and that the safe default for an unknown verb is REGULAR.
- Conjugation Sheet: 알다 / 모르다 (know / not know)TOPIK 2 — A side-by-side sheet for the antonym pair 알다 and 모르다 — a live showcase of the ㄹ-irregular (알다 → 압니다, 아니까) versus the 르-irregular (모르다 → 몰라요), plus the everyday idioms 알겠어요 / 모르겠어요 where -겠- softens rather than points to the future.
- The ㅡ-Drop (으 탈락) TableTOPIK 2 — A fully regular alternation: a stem whose final vowel is ㅡ drops it before any 아/어 ending, and the syllable before the dropped ㅡ then decides harmony — 바쁘다→바빠, 예쁘다→예뻐, 크다→커. The 르-stems are a separate irregular.
- The 아/어 Vowel-Harmony Selection TableTOPIK 1 — The master lookup sheet for choosing 아 vs 어 in every harmony-sensitive ending: if the stem's last vowel is ㅏ or ㅗ, use 아; for everything else use 어; 하 alone takes 여 → 해.