How to Conjugate 모르다 (to not know): 르-irregular Pattern

르 irregular: 르 splits — ㄹ doubles and the vowel changes. 모르 + 아요 → 몰라요.

The Rule

르 irregular: 르 splits — ㄹ doubles and the vowel changes. 모르 + 아요 → 몰라요. 모르다 follows the 르-irregular irregular pattern. This means the verb stem changes when certain endings are added. Don't worry — once you learn this pattern, it applies to many other verbs too.

Why English Speakers Get It Wrong

English verb conjugation is relatively simple — "I eat, he eats, I ate." Korean is more complex because the verb ending changes based on politeness level, tense, AND the verb stem's final vowel or consonant. The 르-irregular pattern is especially tricky because the stem itself changes. English irregular verbs (go→went) change unpredictably, but Korean irregular verbs follow learnable PATTERNS. Once you know the 르-irregular rule, you can predict how all 르-irregular verbs behave.

How It Works

Stem: 모르 Polite present (해요체): 몰라요 Polite past: 몰랐어요 Polite future: 모를 거예요 Formal (합쇼체): 모릅니다 Negative: — Notice how the stem "모르" changes in some forms. This is the 르-irregular pattern in action.

Real Examples

• 몰라요 (morrayo) — "not know (polite present)" • 몰랐어요 (morrateoyo) — "not know (past)" • 모를 거예요 (moreur geoyeyo) — "will not know (future)" • 모릅니다 (moreupnida) — "not know (formal)" • — (—) — "don't not know"

Common Mistakes

❌ 모르아요 (moreuayo) ✅ 몰라요 (morrayo) → 르 → ㄹ is added to previous syllable + 라. This is unique to 르 verbs. ❌ Using the casual form (모르어/아) in formal situations ✅ Use 모릅니다 when speaking to elders, at work, or in official settings → Mixing up politeness levels is one of the most noticeable mistakes foreigners make in Korean.

Quick Tip

Start by mastering the 해요체 (polite) form: 몰라요. This is the form you'll use 90% of the time in daily life. Once it's automatic, add the past (몰랐어요) and future (모를 거예요) to your toolkit. For 르-irregular verbs, make a list of 5 common ones and practice all their forms. The pattern will click after repetition.

모르다: 몰라요 (present) / 몰랐어요 (past) / 모를 거예요 (future)

Examples

몰라요 — morrayo — not know (polite)

몰랐어요 — morrateoyo — not know (past)

모를 거예요 — moreur geoyeyo — will not know

모릅니다 — moreupnida — not know (formal)

— — — — don't not know