Irregular Verbs
Master the most common irregular verb patterns in Korean.
Korean irregular verbs are a small but high-impact category — they appear in some of the most common verbs in the language. The main irregular patterns are: ㄹ verbs (drop ㄹ before certain endings), ㅂ verbs (ㅂ changes to 우 before vowel endings), ㅅ verbs (drop ㅅ before vowel endings), ㄷ verbs (ㄷ changes to ㄹ before vowel endings), 으 verbs (drop 으 before -아/어 endings), 르 verbs (르 doubles before -아/어).
High-frequency irregular verbs you'll encounter early: 듣다 (listen, ㄷ-irregular → 들어요), 돕다 (help, ㅂ-irregular → 도와요), 짓다 (build, ㅅ-irregular → 지어요), 살다 (live, ㄹ-irregular → 살아요 but 사세요 in honorific), 모르다 (not know, 르-irregular → 몰라요). The good news: each irregular pattern is itself regular — once you know that 듣다 is ㄷ-irregular, all conjugations follow predictably. Memorise the verb class along with the dictionary form, not just the meaning.
ㄷ Irregular & ㅂ Irregular
ㄷ irregular: ㄷ changes to ㄹ before a vowel ending. 듣다→들어요, 걷다→걸어요. ㅂ irregular: ㅂ changes to 우/오 before a vowel. 돕다→도와요, 덥다→더워요, 어렵다→어려워요.
ㅡ Drop & 르 Irregular
ㅡ drop: When ㅡ is the last vowel and 아/어 follows, ㅡ drops. 쓰다→써요, 크다→커요. 르 irregular: 르 becomes ㄹㄹ. 모르다→몰라요, 빠르다→빨라요.
How It Works
Korean irregular verbs are not random. Each pattern is a predictable adjustment that happens when a particular stem-final element meets a vowel ending, and once you know which class a verb belongs to, its behaviour is entirely regular within that class.
ㄷ irregular: stem-final ㄷ becomes ㄹ before a vowel. 듣다 gives 들어요, 걷다 gives 걸어요. Note that not every ㄷ-final verb does this — 받다 gives 받아요 regularly — so membership has to be learned per verb.
ㅂ irregular: stem-final ㅂ becomes 우 (or 오 in a couple of verbs) before a vowel. 덥다 gives 더워요, 어렵다 gives 어려워요, 돕다 gives 도와요. This class contains a large share of Korean adjectives, so it pays off quickly.
ㅡ drop: if the final vowel of the stem is ㅡ, it disappears before 아/어. 쓰다 gives 써요, 크다 gives 커요, 바쁘다 gives 바빠요. Which of 아 or 어 appears depends on the vowel in the preceding syllable, if there is one.
르 irregular: 르 doubles the ㄹ. 모르다 gives 몰라요, 빠르다 gives 빨라요, 부르다 gives 불러요.
The common thread is that all four are triggered by a following vowel. Before a consonant ending such as -고 or -지, every one of these verbs behaves regularly.
Where You'll Hear It
These patterns are not edge cases — they cover some of the most frequent words in Korean. 듣다 ('to listen') is ㄷ irregular, and 음악을 들어요 is a sentence you will say often. 걷다 ('to walk') gives 걸어요, which comes up whenever you describe getting somewhere.
The ㅂ class is where the payoff is largest because so many descriptive words belong to it. 덥다, 춥다, 어렵다, 쉽다, 맵다, 무겁다, 가깝다 — weather, difficulty, spiciness and distance are constant topics, and all of them conjugate this way. 매워요 in particular you will use every time you discuss food.
모르다 is arguably the single most useful irregular verb in the language. 몰라요 ('I don't know') is a complete, natural answer, and learners who conjugate it as 모르어요 are immediately marked as guessing.
바쁘다 follows ㅡ drop and gives 바빠요, which is the standard answer to how you have been and the standard excuse for not meeting.
부르다 gives 불러요 and covers both calling someone and singing, so it turns up in social contexts frequently.
Cultural & Language Note
Korean irregular verbs are not random exceptions but the residue of older sound changes, which is why they cluster by final consonant. Every ㅂ-irregular behaves the same way, as does every ㄷ-irregular. Learning them as groups rather than as individual exceptions cuts the memory load dramatically, and after a while you can predict the pattern from the stem alone.
Common Mistakes to Avoid
Not every verb ending in ㅂ or ㄷ is irregular — 좁다 and 받다 conjugate regularly. Learners who apply the pattern to every matching stem produce forms like 받아요 becoming 발아요. There is no shortcut here: the irregular members have to be learned as a list, which is why this lesson front-loads the most frequent ones.
How to Practice This Lesson
Do not try to learn all four classes at once. Take the ㅂ class first, because it contains the most words you already know and the most adjectives you need daily. Conjugate ten ㅂ-irregular adjectives in one sitting and the pattern will stick.
Learn the high-frequency members as fixed forms rather than deriving them. 몰라요, 매워요, 더워요, 바빠요, 들어요 should come out without calculation. Between them they cover a large proportion of the irregular forms you will actually produce.
Test yourself with consonant endings to confirm the trigger. Say 모르고, 맵고, 듣고 and notice that all three are regular. Understanding that the irregularity is conditional rather than inherent makes the whole system less threatening.
Watch for the false members. 받다 and 닫다 end in ㄷ but conjugate regularly, and 좁다 ends in ㅂ but gives 좁아요. Keeping a short list of these exceptions-to-the-exception prevents overgeneralising.