Look at two verbs whose stems end in 르: 다르다 ("to be different") and 따르다 ("to follow / to pour"). They rhyme, they look like twins, and yet their -아/어 forms come out opposite: 다르다 → 달라요 (double ㄹ), 따르다 → 따라요 (single ㄹ). This is the single most confused pair of classes in Korean conjugation, because it hides an exception inside an exception: almost every 르-final stem is a genuine 르-irregular that doubles the ㄹ, but a tiny handful — 따르다, 치르다, 들르다 — are not irregular at all. They are ordinary 으-drop verbs that just happen to end in 르. Getting them right is a matter of learning three words as "exceptions to the exception," and understanding why the ㄹ doubles in one class and not the other.
Two mechanisms, one look
Both classes have a stem ending in 르 = ㄹ + ㅡ. Before a consonant ending or an 으-ending they behave identically — the difference surfaces only in the -아/어 form. What happens there is the whole story.
으-drop imposter (따르다): the stem is 따 + 르. The ㅡ simply drops before 아/어, and the stem's own ㄹ slides forward to become the onset of the ending syllable. Nothing is added.
따르 → drop ㅡ → 따 + ㄹ + 아 → 따라 (one ㄹ)
True 르-irregular (다르다): the ㅡ drops too, but on top of that a second ㄹ is inserted as a batchim on the preceding syllable, and the ending takes 라/러. The ㄹ effectively geminates across the boundary.
다르 → drop ㅡ, copy ㄹ back → 달 + 라 → 달라 (two ㄹ)
So the imposter has one ㄹ (the stem's original ㄹ, resyllabified), and the irregular has two (the copied batchim ㄹ plus the ending's ㄹ). That extra ㄹ is the entire difference.
우리는 생각이 정말 달라요.
urineun saenggagi jeongmal dallayo
We really think differently. (다르다, 르-irregular → 달라요)
회사 규칙을 잘 따라요.
hoesa gyuchigeul jal ttarayo
I follow the company rules well. (따르다, 으-drop → 따라요)
The three imposters — memorize these
Everything in 르 is a real 르-irregular except these three ordinary 으-drop stems. There are only three worth carrying in your head:
| Verb | Meaning | -아/어 form | Why single ㄹ |
|---|---|---|---|
| 따르다 | follow / pour | 따라요 | ㅡ drops, ㄹ slides forward (따 has ㅏ → 아) |
| 치르다 | pay / take (an exam) / undergo | 치러요 | ㅡ drops (치 has ㅣ → 어) |
| 들르다 | drop by / stop by | 들러요 | ㅡ drops (들 has ㅡ → 어) |
Notice how the ending vowel (아 vs 어) still follows ordinary vowel harmony: it is picked by the vowel of the syllable before the dropped ㅡ. 따 has ㅏ (bright) → 아 → 따라; 치 has ㅣ and 들 has ㅡ (both dark) → 어 → 치러, 들러.
잔에 물을 따라 드릴까요?
jane mureul ttara deurilkkayo?
Shall I pour you some water? (따르다 → 따라)
다음 주에 기말시험을 치러요.
da-eum ju-e gimalsiheomeul chireoyo
I take my finals next week. (치르다 → 치러요)
집에 가는 길에 마트에 들러요.
jibe ganeun gire mateu-e deulleoyo
I stop by the supermarket on the way home. (들르다 → 들러요)
어제 친구 집에 잠깐 들렀어요.
eoje chingu jibe jamkkan deulleosseoyo
I dropped by my friend's place briefly yesterday. (들르다, past → 들렀어요)
Everything else in 르 doubles the ㄹ
The default for a 르-final stem is the genuine 르-irregular: the ㄹ doubles. This is the large, productive class — 모르다, 부르다, 빠르다, 고르다, 자르다, 흐르다, 오르다, and dozens more.
| Verb | Meaning | -아/어 form (double ㄹ) |
|---|---|---|
| 모르다 | not know | 몰라요 |
| 부르다 | call / sing | 불러요 |
| 빠르다 | be fast | 빨라요 |
| 고르다 | choose | 골라요 |
| 자르다 | cut | 잘라요 |
| 흐르다 | flow | 흘러요 |
저는 그 사람을 잘 몰라요.
jeoneun geu sarameul jal mollayo
I don't really know that person. (모르다 → 몰라요)
택시 좀 불러 주세요.
taeksi jom bulleo juseyo
Please call a taxi. (부르다 → 불러)
지하철이 버스보다 빨라요.
jihacheori beoseuboda ppallayo
The subway is faster than the bus. (빠르다 → 빨라요)
Before every other ending, they are identical
This is the trap that makes learners let their guard down: outside the -아/어 form, an imposter and a true irregular are indistinguishable. Both are vowel-final stems (르 ends in the vowel ㅡ), so neither takes an 으 buffer, and the ㄹ never doubles anywhere else.
| Ending | 따르다 (imposter) | 다르다 (irregular) |
|---|---|---|
| dictionary | 따르다 | 다르다 |
| -고 | 따르고 | 다르고 |
| -지만 | 따르지만 | 다르지만 |
| -(으)면 | 따르면 | 다르면 |
| -아/어요 | 따라요 | 달라요 |
| past | 따랐어요 | 달랐어요 |
Five of six rows match exactly. Only the bold row splits them apart — which is exactly why you should file the -아/어 form as the identity card of every 르-stem.
Reframing for English speakers
English has irregular verbs (sing → sang, go → went), but it never has two spelling-identical classes that split on one form and merge on all the others. The instinct is to hear "verbs ending in 르 double the ㄹ" as a clean rule and then over-apply it to 따르다 (giving the wrong ×딸라요). Resist that. The honest description is: 르 is a strong default for irregularity, with three lexical hold-outs you memorize by name. There is no phonological cue in the dictionary form that tells you which camp a stem is in — 따르다 and 다르다 differ only in ㄷ vs ㄸ, which has nothing to do with the conjugation. This is genuinely arbitrary, so treat 따르다 / 치르다 / 들르다 like three vocabulary items with a built-in warning label, and assume double-ㄹ for anything else.
Common Mistakes
1. Doubling the ㄹ on an imposter. 따르다 is a plain 으-drop verb — one ㄹ only.
❌ 규칙을 딸라요.
Wrong — 따르다 is not 르-irregular; the ㄹ does not double. It's 따라요.
✅ 규칙을 따라요.
gyuchigeul ttarayo
I follow the rules.
2. Single-ㄹ-ing a true irregular. 모르다 is a real 르-irregular — the ㄹ must double.
❌ 저는 그 사람을 잘 모라요.
Wrong — 모르다 doubles the ㄹ → 몰라요, not ×모라요.
✅ 저는 그 사람을 잘 몰라요.
jeoneun geu sarameul jal mollayo
I don't really know that person.
3. Failing to drop the ㅡ on 들르다. The ㅡ of 들르 vanishes before 어 — you never keep it.
❌ 마트에 들르어요.
Wrong — the ㅡ drops before 어; it's 들러요, not ×들르어요.
✅ 마트에 들러요.
mateu-e deulleoyo
I stop by the supermarket.
4. Doubling the ㄹ on 치르다. Like 따르다, 치르다 is a 으-drop verb — single ㄹ.
❌ 시험을 칠러요.
Wrong — 치르다 is 으-drop → 치러요, not ×칠러요.
✅ 시험을 치러요.
siheomeul chireoyo
I take the exam.
Key Takeaways
- Almost every 르-final stem is a true 르-irregular whose ㄹ doubles before -아/어: 모르다 → 몰라요, 부르다 → 불러요.
- The three imposters — 따르다, 치르다, 들르다 — are ordinary 으-drop verbs: the ㅡ drops and a single ㄹ slides forward → 따라요, 치러요, 들러요.
- The classes split only in the -아/어 form. Everywhere else (-고, -지만, -(으)면, past) they are identical.
- The choice of 아 vs 어 still follows normal harmony (따 → 아 → 따라; 치/들 → 어 → 치러/들러).
- There is no cue in the dictionary form — memorize the three imposters as an exception list and assume double-ㄹ for the rest.
Now practice Korean
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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.
- 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.
- The Rare 러 Irregular: 이르다 → 이르러요, 푸르다 → 푸르러요TOPIK 3 — A tiny class where the 르 stem stays intact and the -아/어 ending surfaces as 러: 이르다 'reach' → 이르러요, 푸르다 → 푸르러요, 누르다 'be deep yellow' → 누르러요. The mirror image of the 르-irregular, and a homograph trap where 이르다 and 누르다 belong to two classes at once.
- 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.