Words Where ㅂ Changes to 우 or 오

Many common Korean verbs and adjectives end in the consonant ㅂ . For many of these words, the ㅂ changes when it meets an ending that starts with a vowel.

When the ㅂ meets a vowel ending, the ㅂ drops, and the vowel 우 appears.

춥다 (to be cold)

어렵다 (to be difficult)

가볍다 (to be light)

This irregular change only happens before vowel endings. If the ending starts with a consonant (like -고 or -지만), the ㅂ stays exactly as it is.

Dictionary Form · + 고 · + 지만

춥다 · 춥고 · 춥지만

어렵다 · 어렵고 · 어렵지만

Let's look at how the newly added 우 combines with common vowel endings.

With -어요

When you add -어요 , the 우 and 어 combine to make 워요 .

춥다 → 추 + 우 + 어요 → 추워요

어렵다 → 어려 + 우 + 어요 → 어려워요

With -(으)면

Because the word now ends in the vowel 우, you use -면 instead of -으면.

춥다 → 추 + 우 + 면 → 추우면

어렵다 → 어려 + 우 + 면 → 어려우면

While most ㅂ irregular words use 우 , there is one very common word that uses 오 instead.

For the verb 돕다 (to help), the ㅂ changes to 오 before the ending -아요.

돕다 + 아요 → 도와요 (I help)

Just like the others, it keeps its ㅂ before a consonant:

돕다 + 고 → 돕고 (help and)

Not every word ending in ㅂ is irregular. Some words are regular and keep their ㅂ even before vowels.

Dictionary Form · + 어요 / 아요