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Adjectives · ㅂ irregular

두껍다 conjugation

to be thick · dukkeopda · sounds like [두껍따]

Short answer: “Thick” in Korean is 두껍다 (dukkeopda). Polite present: 두꺼워요 (dukkeowoyo); past: 두꺼웠어요 (dukkeowosseoyo); future: 두꺼울 거예요. It is a ㅂ irregular adjective.

Opposite: 얇다 — to be thin (paper, clothes)

두껍다 in sentences

All forms of 두껍다

Present
Polite (해요) is the everyday safe choice; formal (합니다) is for news, announcements and work; casual (반말) is for close friends and younger people.
FormKoreanSounds likeRomanized
polite-아/어요두꺼워요[두꺼워요]dukkeowoyo
formal-(스)ㅂ니다두껍습니다[두껍씀니다]dukkeopseumnida
casual-아/어두꺼워[두꺼워]dukkeowo
plain (written)-다두껍다[두껍따]dukkeopda
formal question-(스)ㅂ니까?두껍습니까?[두껍씀니까]dukkeopseumnikka?
Past
FormKoreanSounds likeRomanized
polite-았/었어요두꺼웠어요[두꺼워써요]dukkeowosseoyo
formal-았/었습니다두꺼웠습니다[두꺼웓씀니다]dukkeowotseumnida
casual-았/었어두꺼웠어[두꺼워써]dukkeowosseo
plain (written)-았/었다두꺼웠다[두꺼웓따]dukkeowotda
Future
FormKoreanSounds likeRomanized
polite — will probably be-(으)ㄹ 거예요두꺼울 거예요[두꺼울 꺼예요]dukkeoul geoyeyo
formal-(으)ㄹ 겁니다두꺼울 겁니다[두꺼울 껌니다]dukkeoul geomnida
casual-(으)ㄹ 거야두꺼울 거야[두꺼울 꺼야]dukkeoul geoya
Negative
FormKoreanSounds likeRomanized
not (short)안 …안 두꺼워요[안 두꺼워요]an dukkeowoyo
did not안 …았/었어요안 두꺼웠어요[안 두꺼워써요]an dukkeowosseoyo
not (long)-지 않아요두껍지 않아요[두껍찌 아나요]dukkeopji anayo
Honorific
Add -(으)시- when the subject is someone you respect (a teacher, a customer, an older person) — not yourself.
FormKoreanSounds likeRomanized
honorific — present-(으)세요두꺼우세요[두꺼우세요]dukkeouseyo
honorific — past-(으)셨어요두꺼우셨어요[두꺼우셔써요]dukkeousyeosseoyo
honorific — formal-(으)십니다두꺼우십니다[두꺼우심니다]dukkeousimnida
Connecting
FormKoreanSounds likeRomanized
… and-고두껍고[두껍꼬]dukkeopgo
… so / and then-아/어서두꺼워서[두꺼워서]dukkeowoseo
if …-(으)면두꺼우면[두꺼우면]dukkeoumyeon
… but-지만두껍지만[두껍찌만]dukkeopjiman
because …-(으)니까두꺼우니까[두꺼우니까]dukkeounikka
… and / but (background)-(으)ㄴ데두꺼운데[두꺼운데]dukkeounde
even if …-아/어도두꺼워도[두꺼워도]dukkeowodo
while …-(으)면서두꺼우면서[두꺼우면서]dukkeoumyeonseo
Describing a noun
These go before a noun: “the food (that) I ate”, “a cold day”.
FormKoreanSounds likeRomanized
(that is) …-(으)ㄴ두꺼운[두꺼운]dukkeoun
(that) will …-(으)ㄹ두꺼울[두꺼울]dukkeoul
Useful patterns
FormKoreanSounds likeRomanized
can be …-(으)ㄹ 수 있어요두꺼울 수 있어요[두꺼울 쑤 이써요]dukkeoul su isseoyo
cannot be …-(으)ㄹ 수 없어요두꺼울 수 없어요[두꺼울 쑤 업써요]dukkeoul su eopseoyo
have to be …-아/어야 해요두꺼워야 해요[두꺼워야 해요]dukkeowoya haeyo
it’s OK if it’s …-아/어도 돼요두꺼워도 돼요[두꺼워도 돼요]dukkeowodo dwaeyo
…ly (adverb)-게두껍게[두껍께]dukkeopge
becomes …-아/어지다두꺼워져요[두꺼워저요]dukkeowojeoyo
…ing (noun)-기두껍기[두껍끼]dukkeopgi

How 두껍다 changes

ㅂ irregular: before a vowel, ㅂ turns into 우 — so 두껍 + 어 → 두꺼워요, and -(으) endings use 우: 두꺼우면, 두꺼울. Before a consonant the ㅂ stays: 두껍습니다, 두껍고. Not every ㅂ word does this — 입다 → 입어요 and 잡다 → 잡아요 are regular.

How every verb type works → · Why it sounds like that →

Questions

How do you say “thick” in Korean?

“Thick” is 두껍다 (dukkeopda), pronounced [두껍따]. In a sentence: 이 책은 두꺼워요. — This book is thick.

What is the past tense of 두껍다?

두꺼웠어요 (dukkeowosseoyo) is the polite past tense of 두껍다 (“to be thick”). Formal: 두꺼웠습니다; casual: 두꺼웠어.

How do you say 두껍다 politely?

Everyday polite: 두꺼워요 (dukkeowoyo). Formal: 두껍습니다. Casual, with close friends: 두꺼워.

How do you say “not thick” in Korean?

안 두꺼워요 or 두껍지 않아요. Both mean the same; the first is more common in speech.

Is 두껍다 irregular?

Yes — ㅂ irregular: before a vowel, ㅂ turns into 우 — so 두껍 + 어 → 두꺼워요, and -(으) endings use 우: 두꺼우면, 두꺼울. Before a consonant the ㅂ stays: 두껍습니다, 두껍고. Not every ㅂ word does this — 입다 → 입어요 and 잡다 → 잡아요 are regular.

More ㅂ irregular words like 두껍다

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Forms follow 한글 맞춤법 (Korean spelling rules); pronunciation follows 표준 발음법 and romanization follows 국어의 로마자 표기법 (Revised Romanization). Last updated October 16, 2026. How we check