The 러 irregular is one of the smallest verb classes in Korean — a handful of stems, all ending in 르, that do something no other class does: the stem stays completely untouched, and the ending, which would normally be 아/어, comes out as 러 instead. 이르다 ("to reach / arrive at") becomes 이르러요, 푸르다 ("to be blue-green") becomes 푸르러요. It looks almost identical to the 르 irregular on the page, but it is that class's exact mirror image, and it hides two of the nastiest homograph traps in the language. It is worth learning precisely because it is rare: exams love it, and native speakers will notice instantly if you get 이르러요 wrong.
The mechanism: stem untouched, 어 → 러
In every other -아/어 class, the stem changes and the ending stays 아/어. The 러 irregular flips that. The stem 르 is left exactly as written, and only the ending's vowel is altered — 어 is replaced by the whole syllable 러:
이르 + 어 → (stem kept) → 이르 + 러 → 이르러
푸르 + 어 → 푸르 + 러 → 푸르러
Compare that with a true 르-irregular, where the ㅡ drops and a ㄹ doubles: 모르 → 몰라. The two could not be more different in what they touch.
봄 산이 참 푸르러요.
bom sani cham pureureoyo
The spring mountains are so green. (푸르다 → 푸르러요; literary)
하늘이 눈부시게 푸르렀어요.
haneuri nunbusige pureureosseoyo
The sky was dazzlingly blue. (푸르다, past → 푸르렀어요)
The whole membership
This is essentially a closed list — you can learn all of it. The members are stems of reaching and a few colors.
| Verb | Meaning | -아/어 form | Register |
|---|---|---|---|
| 이르다 | reach / arrive at / amount to | 이르러요 | formal / written |
| 푸르다 | be blue / green (of nature) | 푸르러요 | literary / elevated |
| 누르다 | be deep yellow | 누르러요 | literary / rare |
| 노르다 | be yellowish | 노르러요 | archaic / literary |
The color verbs are elevated: in everyday speech Koreans say 파랗다 for blue and 노랗다 for yellow. 푸르다 and 누르다 belong to poetry, the national anthem, weather-lyrical writing, and set descriptions of nature. 이르다 "reach" is the workhorse of the group and appears constantly in formal and written Korean — 결론에 이르다 ("reach a conclusion"), 합의에 이르다 ("reach an agreement"), 정상에 이르다 ("reach the summit").
오랜 논의 끝에 결론에 이르렀어요.
oraen nonui kkeute gyeollone ireureosseoyo
After long discussion, we reached a conclusion. (formal; 이르다 → 이르렀어요)
정상에 이르러서야 도시가 한눈에 들어왔어요.
jeongsang-e ireureoseoya dosiga hannune deureowasseoyo
Only upon reaching the summit did the whole city come into view. (literary)
가을이 되니 들판이 누르러요.
ga-euri doeni deulpani nureureoyo
As autumn comes, the fields turn deep yellow. (literary; 누르다 → 누르러요)
Before any other ending, 러-irregular stems are perfectly regular vowel-final stems — the 르 stays, no 으 is inserted: 이르고, 이르지만, 이르면, 푸르고, 푸르니까. The irregularity lives only in the -아/어 form, exactly as in the 르 class.
The homograph trap: one spelling, two classes
Here is where the 러 irregular earns its reputation. Two of its members are spelled identically to common 르-irregular verbs of a different meaning — so the same dictionary form conjugates two different ways depending on which word you mean.
이르다 — three meanings, two classes
| 이르다 means… | Class | -아/어 form |
|---|---|---|
| reach / arrive at | 러-irregular | 이르러요 |
| be early | 르-irregular | 일러요 |
| tell on / report / inform | 르-irregular | 일러요 |
So 이르러요 means "reaches," while 일러요 means either "is early" or "tattles" — three meanings, and only the "reach" sense takes the 러 pattern.
아직 포기하기엔 일러요.
ajik pogihagi-en illeoyo
It's still too early to give up. (이르다 'be early', 르-irregular → 일러요)
동생이 자꾸 엄마한테 일러요.
dongsaeng-i jakku eommahante illeoyo
My little sibling keeps telling on me to Mom. (이르다 'tell on', 르-irregular → 일러요)
형이 나를 엄마한테 다 일렀어요.
hyeong-i nareul eommahante da illeosseoyo
My brother told Mom everything on me. (이르다 'tell on', past → 일렀어요)
누르다 — press vs. deep yellow
The same split hits 누르다. In its everyday meaning "to press / push," it is a garden-variety 르-irregular → 눌러요. Only in the literary color sense "be deep yellow" is it 러-irregular → 누르러요.
엘리베이터 버튼을 눌러 주세요.
ellibeiteo beoteuneul nulleo juseyo
Please press the elevator button. (누르다 'press', 르-irregular → 눌러)
Reframing for English speakers
English does have spelling collisions that conjugate differently — lie (recline) → lay vs. lie (tell falsehoods) → lied. Korean's 이르다 is the same phenomenon, just with three meanings fanning into two classes. What English does not have is the 러 mechanism itself: an ending vowel that mutates because of the specific lexical class of the stem, while the stem sits untouched. Don't try to rationalize why "reach" adds 러 and "be early" doubles the ㄹ — there is no synchronic logic, only history. Treat the 러 irregular as a four-word closed list (이르다-reach, 푸르다, 누르다-yellow, 노르다), memorize each with its 러 form, and let the homograph warning fire whenever you see 이르다 or 누르다.
Common Mistakes
1. Treating 이르다 "reach" as a 르-irregular. The reach sense is 러-irregular — the stem stays, 러 is added.
❌ 드디어 목적지에 일러요.
Wrong — 이르다 'reach' is 러-irregular → 이르러요; 일러요 would mean 'is early / tattles'.
✅ 드디어 목적지에 이르러요.
deudieo mokjeokji-e ireureoyo
We finally reach the destination.
2. Treating 푸르다 as a 르-irregular. Color 푸르다 never doubles the ㄹ.
❌ 하늘이 풀러요.
Wrong — 푸르다 is 러-irregular → 푸르러요, not ×풀러요.
✅ 하늘이 푸르러요.
haneuri pureureoyo
The sky is blue.
3. Treating 누르다 "press" as a 러-irregular. The press sense is an ordinary 르-irregular.
❌ 초인종을 누르러요.
Wrong — 누르다 'press' is 르-irregular → 눌러요; only 누르다 'be deep yellow' is 러-irregular.
✅ 초인종을 눌러요.
choinjong-eul nulleoyo
I press the doorbell.
4. Applying the 러 pattern to 이르다 "be early." Only the "reach" sense takes 러.
❌ 아직 시간이 이르러요.
Wrong — 이르다 'be early' is 르-irregular → 일러요, not ×이르러요.
✅ 아직 시간이 일러요.
ajik sigani illeoyo
It's still early.
Key Takeaways
- The 러 irregular keeps the 르 stem intact and turns the -아/어 ending into 러: 이르다 → 이르러요, 푸르다 → 푸르러요, 누르다(yellow) → 누르러요.
- It is the mirror image of the 르 irregular: 르 doubles the ㄹ and shortens (몰라), 러 preserves the stem and lengthens (이르러).
- The class is a closed list of four: 이르다(reach), 푸르다, 누르다(yellow), 노르다 — the colors being literary.
- Homograph traps: 이르다 "reach" is 러 (이르러요) but "be early / tell on" is 르 (일러요); 누르다 "be deep yellow" is 러 (누르러요) but "press" is 르 (눌러요). Meaning picks the class.
- Only the -아/어 form is irregular; before other endings these are plain vowel-final stems (이르고, 이르면).
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Start learning Korean→Related Topics
- The 르 Irregular: 모르다 → 몰라요TOPIK 1 — The high-frequency 르 irregular — before an 아/어 ending the 으 of 르 drops and an extra ㄹ pushes back onto the previous syllable (모르다 → 몰라요, 빠르다 → 빨라요), with 라/러 chosen by vowel harmony.
- 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 으 Drop: 쓰다 → 써요, 크다 → 커요TOPIK 1 — Any stem whose last vowel is ㅡ loses that ㅡ before an -아/어 ending. For a one-syllable ㅡ stem there is no preceding vowel, so it always defaults to 어: 쓰다 → 써요, 크다 → 커요, 끄다 → 꺼요. The most predictable of all the 'irregular' classes.
- 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.