The Eu-Irregular & Reu-Irregular

When a verb or adjective stem ends in the vowel 'ㅡ (eu)', the 'ㅡ' drops before '-아요/-어요 (-ayo/-eoyo)'. This is called the eu-irregular.

Dropping 'ㅡ (eu)'

Look at the vowel of the syllable right before 'ㅡ (eu)'. If that vowel is 'ㅏ (a)' or 'ㅗ (o)', add '-아요 (-ayo)'; otherwise add '-어요 (-eoyo)'. If there is no preceding syllable, use '-어요 (-eoyo)'.

Dictionary	Conjugated	Meaning
바쁘다 (bappeuda)	바빠요 (bappayo)	to be busy
예쁘다 (yeppeuda)	예뻐요 (yeppeoyo)	to be pretty
크다 (keuda)	커요 (keoyo)	to be big
쓰다 (sseuda)	써요 (sseoyo)	to write / use

오늘은 일이 많아서 너무 바빠요.

oneur-eun ir-i manaseo neomu bappayo.

I'm very busy today because there is a lot of work.

이 꽃이 정말 예뻐요.

i kkoch-i jeongmal yeppeoyo.

This flower is really pretty.

The Reu-Irregular

When a stem ends in '르 (reu)', the 'ㅡ' drops and an extra 'ㄹ (r)' is added: 모르다 → 몰라요 (mollayo), 빠르다 → 빨라요 (ppallayo).

Dictionary	Conjugated	Meaning
모르다 (moreuda)	몰라요 (mollayo)	to not know
부르다 (bureuda)	불러요 (bulleoyo)	to call / sing
다르다 (dareuda)	달라요 (dallayo)	to be different

미안해요, 저는 그 사람을 몰라요.

mianhaeyo, jeo-neun geu saram-eul mollayo.

Sorry, I don't know that person.

지하철이 버스보다 빨라요.

jihacheor-i beoseu-boda ppallayo.

The subway is faster than the bus.

쌍둥이지만 성격이 서로 달라요.

ssangdung-ijiman seonggyeog-i seoro dallayo.

They are twins, but their personalities are different from each other.

오늘은 시간이 없어서 너무 슬퍼요.

oneur-eun sigan-i eopseoseo neomu seulpeoyo.

I have no time today, so I'm very sad.

노래방에서 노래를 불러요.

noraebang-eseo norae-reul bulleoyo.

I sing a song at the karaoke room.

할머니가 머리가 하얘서 예뻐요.

halmeoni-ga meori-ga hayaeseo yeppeoyo.

My grandmother is pretty with her white hair.

The Eu-Irregular & Vowel Harmony

After 'ㅡ (eu)' drops, look at the vowel of the syllable right before it: 아프다 → 아파요 (apayo, preceding vowel 'ㅏ'), 기쁘다 → 기뻐요 (gippeoyo, preceding vowel 'ㅣ').

Common mistake: with one-syllable stems like 쓰다 (sseuda) or 크다 (keuda), there is no preceding syllable, so always use '-어요 (-eoyo)': 쓰다 → 써요 (sseoyo, not 싸요), 크다 → 커요 (keoyo).

💡 Tip: Tip: the reu-irregular still follows vowel harmony. If the preceding vowel is 'ㅏ (a)' or 'ㅗ (o)', use '-ㄹ라요 (-llayo)'; otherwise '-ㄹ러요 (-lleoyo)': 빠르다 → 빨라요, 부르다 → 불러요.

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