Korean Irregular Conjugation Rules: How to Recognize Each Class

What you'll learn

• Explain what makes a Korean verb irregular in one sentence.
• Name the class of any dictionary-form verb or adjective with a four-question decision tree.
• Confirm the class by conjugating before 아/어 and before 으.
• List which classes follow a pure rule and which need a memorised word list.

Prerequisites: you can make the polite present of a regular verb with the present tense recipe, and you know the stem-plus-ending idea from how Korean conjugation works. Time: about 35 minutes.

The first section explains what "irregular" means in Korean, which is not what it means in English.

What Makes a Korean Verb Irregular?

A Korean verb or adjective is irregular when its stem changes shape before certain endings. The stem is the dictionary form minus 다: 먹다 → 먹, 듣다 → 듣. A regular stem never changes, so 먹 + 어요 is simply 먹어요. An irregular stem changes in a fixed way: 듣 + 어요 becomes 들어요, with ㄷ turned into ㄹ.

The key difference from English is predictability. English irregular verbs must be learned one by one: "go, went", "see, saw". Korean irregular verbs come in classes, and every member of a class changes the same way. If you know that 덥다 ("to be hot") gives 더워요, you also know 춥다 ("to be cold") gives 추워요, because both are in the ㅂ class.

Each class is named after the letter that changes: the ㅂ irregular, the ㄷ irregular, and so on. 하다 verbs are sometimes counted as an eighth class (the 여 irregular), but they follow their own simple rule, 하 + 여 → 해, and are taught separately. The next section shows how to predict the class from the dictionary form alone.

How Do You Recognize an Irregular Verb from Its Stem?

Look at the last letter of the stem and answer four questions in order. The first answer that applies names the class or tells you the verb is regular.

1. Does the stem end in a vowel? If the last syllable is 르, go to the 르 check (question 4). If it ends in ㅡ, it is in the ㅡ class: 쓰다, 바쁘다. If it is 하, use the 하다 rule. Any other vowel stem is regular, with ordinary contraction: 가다 → 가요, 보다 → 봐요.
2. Does the stem end in ㄹ? Then it is in the ㄹ class, without exception: 살다, 만들다, 길다.
3. Does the stem end in ㅂ, ㄷ, ㅅ or ㅎ? Then the word may be irregular, and you need the list. Most ㅂ adjectives and most single-ㅎ adjectives are irregular; only a handful of ㄷ and ㅅ verbs are.
4. Does the stem end in 르? Then it is almost always a 르 irregular: 모르다 → 몰라요. Three common verbs only drop ㅡ instead (따르다, 치르다, 들르다), and 이르다 "reach" and 푸르다 belong to the rare 러 class.

Any stem that ends in another consonant, such as ㄱ (먹다), ㅁ (감다), ㅈ (잊다), ㄴ (신다) or ㅌ (같다), is regular.

The table already hints at an important split: some rows say "none" and some say "check". The next section explains that difference.

Which Irregular Classes Are Rule-Based and Which Need a List?

Three classes follow a pure rule: every ㄹ stem, every ㅡ stem and nearly every 르 stem behaves the same way, so the dictionary form is enough. The other four, ㅂ, ㄷ, ㅅ and ㅎ, are list-based: the stem shape only tells you to check, because regular look-alikes exist.

The class sizes below come from the 474 verbs and adjectives on this site's verb dictionary list, a selection of useful words rather than a count of the whole language. They show how much memorising each class really needs.

For the small ㄷ and ㅅ classes, learning the irregular members is easier than learning the exceptions. The ㄷ verbs on this site's list are 듣다, 걷다 (walk), 묻다 (ask), 깨닫다, 싣다 and 알아듣다; the common ㅅ verbs are 낫다, 짓다, 붓다 and 잇다, plus 긋다 and 젓다. Almost every other -ㄷ다 or -ㅅ다 verb a learner meets is regular; a few rarer words, such as 붇다 (swell) and 일컫다 (call), are ㄷ-irregular too. Watch the homographs: 묻다 "bury" and 걷다 "roll up" are regular (묻어요, 걷어요). For the full ㄷ list with forms, see ㄷ irregular explained. A list tells you what to suspect; the next section gives you a way to confirm it.

Korean Irregular Conjugation Rules: Two Quick Tests

Two test forms reveal any class. Test 1: add the polite present -아요/-어요. Test 2: add -(으)면 ("if"). Compare each result with what a regular stem would give, and note which test shows the change.

The pattern makes the tests diagnostic. If both forms change, the class is ㅂ, ㄷ, ㅅ or ㅎ, and the kind of change tells you which: 우 for ㅂ, ㄹ for ㄷ, a lost consonant for ㅅ, ㅐ for ㅎ. If only Test 1 changes, it is 르 or ㅡ: an extra ㄹ means 르. If only Test 2 changes (살면, not 살으면), it is ㄹ, and a third form confirms it: before -는, the ㄹ disappears (사는).

Worked Example: 걷다

1. Last letter of the stem: 걷 ends in ㄷ, so question 3 applies: check.
2. Test 1: 걷 + 어요. A regular verb would give 걷어요, but the correct form for "walk" is 걸어요. The stem changed.
3. Test 2: 걸으면, not 걷으면. The stem changed again.
4. Read the result: both tests change, and ㄷ became ㄹ, so 걷다 ("to walk") is ㄷ-irregular. The homograph 걷다 "to roll up" (sleeves) is regular: 소매를 걷어요.

You'll know it worked when the class you named predicts both test forms. If it does not, the word is probably a look-alike, which is the subject of regular verbs that look irregular. With the method in place, the next question is how many classes there are in total.

How Many Irregular Classes Does Korean Have?

Learners usually work with seven classes: ㅂ, ㄷ, ㅅ, 르, ㅎ, ㅡ and ㄹ. Korean school grammar (학교 문법) counts differently, and the difference explains why Korean and English textbooks disagree.

Korean school grammar counts the ㄹ and ㅡ changes as regular. It calls them ㄹ 탈락 and 으 탈락 ("deletion") and treats them as automatic rules, because every stem of that shape behaves the same way. It counts as irregular only the changes that some words make and others do not: ㅅ, ㄷ, ㅂ, 르 and 우, where the stem changes; 여 and 러, where the ending changes; and ㅎ, where both change.

Both systems describe the same forms, so neither is wrong. This site follows the learner convention and calls ㄹ and ㅡ irregular classes, because a beginner needs to learn them in the same way as the others. A Korean textbook that says "으 탈락 is regular" is describing the ㅡ irregular explained on this site under another name. Counting classes matters less than knowing which ones to learn first, which the next section answers.

Which Irregular Verbs Should You Learn First?

Learn the ten words below first. Each is used in the first weeks of Korean, and together they cover five of the seven classes. The trigger line says what to remember.

The ㄹ class is missing from this list only because its polite present looks regular (살아요). Its changes show up in 사는 and 삽니다, which you will meet with the -는 and formal endings. The ㅅ class (낫다, 짓다) is small and can wait until you need it. The rest of the system can wait longer, as the next section shows.

Rare Classes You Can Ignore at First

A few classes affect only a handful of words. A beginner can recognise them when they appear and learn them later.

• 러 irregular: the ending -어 becomes -러 after 이르다 "to reach" and 푸르다 "to be blue-green": 이르러요, 푸르러요. Do not confuse 이르다 "reach" with 이르다 "be early", which is a 르 irregular: 일러요.
• 우 irregular: a single verb, 푸다 "to scoop", which gives 퍼요.
• 여 irregular: 하다 and every 하다 verb: 하 + 여 → 해요. This is the most frequent "irregular" of all, but the present tense recipe treats it as its own simple rule.
• Older imperative classes: older grammars also list special imperative endings such as 가거라 and 오너라. They appear in literature and songs, not in everyday speech.

None of these needs a decision tree, because the words are few enough to learn as vocabulary. What does need attention are the wrong beliefs that make learners misclassify common words, covered next.

Common Misconceptions

Four beliefs cause most classification errors.

• Learners often assume "irregular" means "unpredictable". Actually every class follows one fixed change. Knowing 덥다 → 더워요 predicts 춥다 → 추워요.
• Learners often assume every ㅂ, ㄷ or ㅅ stem is irregular. Actually 입다, 받다 and 씻다 are regular. Wrong: 이워요, 발아요, 씨어요. Right: 입어요, 받아요, 씻어요.
• Learners often treat every 르 verb as 르 irregular. Actually 따르다, 치르다 and 들르다 follow the ㅡ rule. Wrong: 딸라요. Right: 따라요.
• Learners often assume ㄹ verbs are regular because 살아요 looks regular. Actually the ㄹ drops before ㄴ, ㅂ and ㅅ. Wrong: 살는 사람, 살습니다. Right: 사는 사람, 삽니다.

An honest limit: the decision tree covers the words a learner meets through roughly intermediate level. Some rare or literary verbs, and homographs such as 묻다 "ask" (irregular) and 묻다 "bury" (regular), can only be settled by meaning or a dictionary. The Korean verb conjugator on this site shows the class for every word in its reviewed list and refuses to guess for words outside it.

Practice: Classify 12 Verbs

Name the class (or "regular") for each word, then confirm it with Test 1. Answers follow.

1. 춥다
2. 잡다
3. 빠르다
4. 걷다
5. 만들다
6. 아프다
7. 하얗다
8. 짓다
9. 씻다
10. 좋다
11. 따르다
12. 받다

Answer key

If you got 10 or more right, the decision tree works for you. Most errors fall on items 2, 9, 11 and 12, the look-alikes.

Next Steps after the Irregular Rules

With the Korean irregular conjugation rules for spotting each class in hand, study the classes one at a time, starting with the largest, the ㅂ irregular. Then use the irregular verbs chart as a one-page reference for all seven.

What this page does not cover. It names each class and how to recognise it, but the full rules, word lists and practice for each class are on the class pages. About this page. Last updated 2026-10-09. The Korean text and conjugated forms were drafted with AI assistance and cross-checked with the site's rule-based conjugation engine; the Korean reviewer checks every lesson before publication. Romanization follows the Revised Romanization of Korean and is only a learning aid.

Frequently Asked Questions

Does Korean have irregular verbs? Yes. Korean has about seven common irregular classes, named after the letter that changes: ㅂ, ㄷ, ㅅ, 르, ㅎ, ㅡ and ㄹ. Unlike English irregular verbs, each class changes in one fixed way, so 덥다 → 더워요 predicts 춥다 → 추워요. Once you know the class, the forms are as predictable as regular ones.

How many irregular verbs are there in Korean? There is no single official count, but the number a learner needs is small. Of the 474 verbs and adjectives on this site's verb dictionary list, 109 belong to the seven classes and 3 to the rare 러 and 우 classes. The ㅂ class is the largest with 36 words; ㄷ has 6 and ㅅ has 4.

Is 좋다 irregular? No. 좋다 ("to be good") is regular even though its stem ends in ㅎ: 좋아요, 좋았어요, 좋은. Most other adjectives with a single final ㅎ, such as 그렇다 and 빨갛다, are ㅎ-irregular, which is why 좋다 is the classic trap. Its ㅎ is silent before a vowel, so 좋아요 is said [조아요].

Can I guess whether a verb is irregular from the dictionary form? Partly. For ㄹ, ㅡ and most 르 stems the dictionary form is enough, because every such stem behaves the same way. For ㅂ, ㄷ, ㅅ and ㅎ stems it only tells you to check: 듣다 is irregular but 받다 is not. A dictionary entry or the two quick tests settle the doubtful cases.

Why are irregular verbs important for beginners? Because many first-week words are irregular. 듣다 (listen), 걷다 (walk), 모르다 (not know), 쓰다 (write), 덥다 (hot), 춥다 (cold) and 그렇다 (be so) all change their stem in the polite present. A learner who skips the classes cannot say 들어요, 몰라요 or 추워요 correctly in a basic conversation.

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