Knowing and Not Knowing
알다 vs. 모르다
In Korean, "to not know" is a completely separate verb, 모르다 , rather than a negative form of 알다 (to know). You use these verbs for people, places, methods, and facts.
Common Combinations
사람을 알다 : to know a person
길을 모르다 : to not know the way
방법을 알다 : to know the method
Notice that they commonly combine with the object marker 을/를 .
Remembering and Forgetting
기억하다 vs. 잊다
When you talk about retaining information in your memory, use 기억하다 (to remember). When you lose that information, use 잊다 (to forget).
Common Combinations
이름을 기억하다 : to remember a name
약속을 기억하다 : to remember an appointment or promise
비밀번호를 잊다 : to forget a password
잊다 vs. 잊어버리다
Emphasizing the Mistake
You will frequently hear 잊어버리다 instead of just 잊다 . Adding -아/어버리다 to a verb gives the feeling that an action is completely finished, often carrying a slight sense of regret or finality.
Form · Meaning
잊었어요 · I forgot.
잊어버렸어요 · I completely forgot (and I'm sorry or frustrated).
In daily conversation, 잊어버렸어요 is the most natural way to say you forgot your password, an appointment, or someone's name.
Common Mistake: "I don't know" vs. "I forgot"
Did you ever know it?
A common beginner mistake is using 몰라요 (I don't know) when you actually mean 잊어버렸어요 (I forgot).
Nuance Warning: If someone asks for your friend's phone number and you knew it before but can't recall it now, you must say 잊어버렸어요 .
Using 몰라요 sounds like you never had their number in the first place, which can sound dismissive or unnatural in Korean.