Core Grammar Rule: -(으)ㄹ 수 있어요/없어요
This pattern is used to express ability (can/can't) or possibility (it is possible/impossible). It's one of the most common ways to talk about what you are able to do.
Meaning & Usage
Meaning: It attaches to a verb stem to mean "can (do)" or "cannot (do)". -(으)ㄹ 수 있어요 means "can," and -(으)ㄹ 수 없어요 means "cannot."
When to use: Use it to talk about your skills (like driving or cooking), physical capabilities (like eating spicy food), or situational possibilities (like being able to go to a party this weekend).
Conjugation Rules
Rule: The choice between -ㄹ 수 있다/없다 and -을 수 있다/없다 depends on whether the verb stem ends in a vowel or a consonant.
Vowel or ㄹ: Add -ㄹ 수 있어요/없어요 directly to the verb stem. (e.g., 가다 → 갈 수 있어요 / 만들다 → 만들 수 있어요)
Consonant: Add -을 수 있어요/없어요 to the verb stem. (e.g., 먹다 → 먹을 수 있어요)
Vowel/ㄹ: -ㄹ 수 있어요/없어요 / Consonant: -을 수 있어요/없어요
Native Nuance & Mistakes
Korean has another common way to say "can't": 못. Understanding the difference between 못 and -(으)ㄹ 수 없다 is key to sounding natural.
못 + Verb: Inability or Lack of Skill
Context: 못 is often used to express that you can't do something because you lack the skill, ability, or for some external reason that prevents you. It's very common in spoken Korean and often feels a bit more direct than -(으)ㄹ 수 없다.
Example: 저는 운전을 못 해요. (I can't drive - because I don't know how). / 시끄러워서 잠을 못 잤어요. (I couldn't sleep because it was noisy.)
-(으)ㄹ 수 없다: Impossibility or Lack of Permission
Context: -(으)ㄹ 수 없다 can also mean a lack of ability, but it often carries a stronger nuance of "it is impossible" or "I am not allowed to." It can sound slightly more formal or emphatic than 못.
Example: 여기서는 담배를 피울 수 없어요. (You can't smoke here - it's not allowed). / 지금은 바빠서 갈 수 없어요. (I can't go because I'm busy - it's impossible right now).
Do: 저는 수영을 못 해요. (O) / Also Do: 저는 수영을 할 수 없어요. (O)