I’m learning to conjugate into past tense in formal language (합쇼체). From what I’ve learned, if a stem ends in a consonant, you add “았습니다” or “있습니다” after it depending on the vowel before.

However, I’ve seen 춥다 conjugated into 추었습니다 , dropping the ㅂ altogether.

My question is: - is 춥다 an anomaly for doing this or is there another rule during conjugation that I need to know (for when to drop ending consonants)?

  • 1
    A bit of spelling checks: “있습니다” → “-습니다,” “추었습니다” → “추습니다.” Nov 15, 2018 at 12:25
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    Just an off-topic note: 춥다 is an irregular Korean adjective meaning "to be cold."
    – Klmo
    May 24, 2019 at 11:43
  • @Klmo Off-topic? No, that’s pretty valid and helpful comment. But to be more precise, it means just “cold,” because it’s an adjective. Jun 21, 2021 at 21:34

1 Answer 1


Hoping someone else would explain it in detail, let me just give you a tiny bit of info about this phenomenon.

Is “춥다” an irregular adjective?

Yes, along with other “-ㅂ” stem adjectives/verbs except for some. We can't say every such adjective/verb is, but a bunch are.

ㅂ irregular inflection

It’s called “ㅂ irregular inflection (ㅂ 불규칙 활용).” It’s inflection where a stem’s final “ㅂ,” as in “ㅂ” in “춥-,” becomes an “ㅗ” or “ㅜ” before an inflection suffix with no initial consonant, such as “-었-.” E.g. “춥다” → “추웠다” [“추”+(“ㅂ-”→“ㅜ-”)+“-었-”+“-다”].

Why does this happen?

Such a “ㅂ” was originally a “ㅸ” (unused nowadays), which likely had the /v/ sound at the initial position of a syllable and the /p/ sound (with no audible release) at the final. Later, the /v/ sound shifted to the /w/ sound.

(“추ᇦ-”+“-어”) → “추ᄫᅥ” (Since “-어” has no initial consonant, the “ㅸ” takes the initial position here.) → “추워”

Fun fact: some dialects still have this sound.

The Kyungsang dialect. They say “추ᄫᅳ라 /choovɾa/” for the standard equivalent “추워라 /choowoɾa/.”

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    Thank you very much for your reply. This answers my question perfectly and in so much detail! I shall be sure to remember this phenomenon in future. :)
    – Amethyst
    Nov 16, 2018 at 0:22
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    I think this is a perfect answer for language learners. I would just add that these verbs and adjectives have the same phenomenon: 굽다, 눕다, 덥다, 돕다, 괴롭다, 가렵다, 그립다, 아름답다, 무섭다, 아니꼽다, -스럽다.
    – Klmo
    May 24, 2019 at 11:50

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