Irregulars¶

As if the conjugation rules based on vowels weren't hard enough, there are some verbs that undergo additional transformation based on the last consonant (or if the last syllable is 르). These are called irregulars.

There are six common patterns shown here, each triggered by certain endings. So far, we've only encountered a few kinds of endings. But there will be more endings later on in this text. So the rules here are stated in general, making them useful later on too.

In particular, besides 아/어, there's only one more class of endings that starts with a vowel, the 으-endings. We'll meet these later, but -(으)면 ("if") is one such example. Here is a summary table:

ㅂ to 우 before 아/어/으¶

• Adjectives: Almost all of them.
  • Most common exceptions: 좁다 ("to be narrow") → 좁아.
• Verbs: Almost none.
  • Most common exceptions: 눕다 ("to lie down") → 누워, 줍다 ("to pick up") → 주워, and 굽다 ("to grill") → 구워.

Before 아/어/으, a final ㅂ turns into 우, which then merges with the ending as usual (e.g., ㅜ+ㅓ=ㅝ). With 아/어 endings, the ending is always 어, even if the stem has ㅏ (고맙다 → 고마워). With 으-endings, the 으 disappears after 우: 어렵다 → 어려우면.

There are two ㅂ words that change to 오 instead before 아/어: 돕다 ("to help") → 도와 and 곱다 ("to be pretty") → 고와. (With 으-endings, they still use 우: 도우면.)

ㄷ to ㄹ before 아/어/으¶

• Adjectives: Never. (There are hardly any adjectives ending in ㄷ anyway.)
• Verbs: Maybe half of the common ones.
  • Common examples: 듣다 → 들어, 걷다 → 걸어, 묻다 ("to ask") → 물어.
  • Common non-examples: 받다 ("to receive") → 받아, 닫다 ("to close") → 닫아, 믿다 ("to believe") → 믿어.

Before 아/어/으, the final ㄷ turns into ㄹ. With 으-endings, the 으 stays: 듣다 → 들으면.

Interestingly, there's another 묻다 meaning "to bury" that is regular: 묻어. So these are two different words with the same dictionary form.

ㅅ deletion before 아/어/으¶

• Adjectives: Just 낫다 ("to be better"), which is about the only adjective ending in ㅅ.
• Verbs: Maybe half of the common ones.
  • Common examples: 짓다 → 지어, 낫다 → 나아, 붓다 → 부어.
  • Common non-examples: 웃다 ("to laugh") → 웃어, 씻다 ("to wash") → 씻어, 벗다 ("to take off") → 벗어.

Before 아/어/으, the final ㅅ disappears. Unusually, the syllables stay separate afterwards. So the merge rules do not apply (짓다 → 지어, not 져), and with 으-endings, the 으 stays (짓다 → 지으면, not 지면).

ㄹ doubling in 르 before 아/어¶

• Adjectives: Almost all of them.
  • Most common exceptions: 푸르다 ("to be sea blue") → 푸르러.¹
• Verbs: Almost all of them.
  • Most common exceptions: 따르다 ("to follow") → 따라 and 치르다 ("to pay; to take (an exam)") → 치러. This is the usual ㅡ rule.

For stems ending in 르, before 아/어, the ㅡ still disappears, but an extra ㄹ is added to the syllable before it. So 모르다 becomes 몰라, not 모라. Other endings, including 으-endings, are unaffected: 모르면.

This rule only makes sense if the syllable before 르 doesn't already end in a consonant. This turns out to be true for almost every 르 stem.²

ㅎ deletion in adjectives before 아/어/으¶

• Adjectives: Almost all of them.
  • Most common exceptions: 좋다 ("to be good") → 좋아.
• Verbs: Never.

For adjectives ending in ㅎ, the ㅎ disappears. If the vowel was 아/어, it becomes ㅐ (or ㅒ, if it was ㅑ). With 으-endings, both ㅎ and 으 disappear: 그렇다 → 그러면, 빨갛다 → 빨간 (from -(으)ㄴ).³

ㄹ deletion before ㄴ, ㄹ, ㅂ, ㅅ¶

• Adjectives: All of them, without exception.
• Verbs: All of them, without exception.

The previous irregulars were only triggered before 아/어/으. The ㄹ deletion rule is the only one that is always triggered before consonants. It also is unusual in that it has no exceptions (so the name "irregular" is slightly misleading here.)

The rule is: if the stem ends in ㄹ, the ㄹ disappears before any ending that starts with ㄴ, ㄹ, ㅂ, or ㅅ. So far, you have only seen ㄴ endings for verbs in diary form, and ㅂ endings for formal conjugation, so those are the examples we give:

(길다 is an adjective, so its diary form is the same as its dictionary form and no special rule applies.)

One additional wrinkle: with 으-endings, ㄹ stems drop the 으 as if they ended in a vowel: 살다 → 살면. If what's left starts with ㄴ, ㄹ, or ㅅ, the ㄹ then disappears as usual: 살다 → 사세요 (from -(으)세요).