-(으)ㄹ 수 있다 / -(으)ㄹ 줄 알다
Ability Expressions
-ㄹ 수 있다 means 'can' (ability or possibility).
-ㄹ 줄 알다 means 'know how to' (a learned skill).
How It Works
Understanding the subtle difference between these two patterns is key to sounding more natural in Korean.
1. -ㄹ 수 있다/없다: General Ability & Possibility
This is the most common way to say 'can' or 'cannot'. It attaches to verb stems.
- Verb stem ending in a vowel + -ㄹ 수 있다/없다 (e.g., 가다 → 갈 수 있다)
- Verb stem ending in a consonant + -을 수 있다/없다 (e.g., 먹다 → 먹을 수 있다)
It's used in two main contexts:
A) General Ability: The inherent or physical capacity to do something.
저는 100미터를 뛸 수 있어요. (I can run 100 meters.)
B) Possibility or Permission: Whether a situation allows for an action.
지금 회의 중이라서 전화를 받을 수 없어요. (I'm in a meeting now, so I can't receive the call.)
여기서 쉬어도 돼요? → 네, 쉴 수 있어요. (Can I rest here? → Yes, you can rest.)
2. -ㄹ 줄 알다/모르다: Learned Skill or Knowledge of a Fact
This pattern is more complex as it has two distinct meanings. It also attaches to verb stems with the same rules as above.
- Verb stem ending in a vowel + -ㄹ 줄 알다/모르다 (e.g., 운전하다 → 운전할 줄 알다)
- Verb stem ending in a consonant + -을 줄 알다/모르다 (e.g., 만들다 → 만들 줄 알다)
A) Learned Skill: 'To know how to do something'. This is the meaning most often compared with -ㄹ 수 있다.
저는 한국 요리를 만들 줄 알아요. (I know how to make Korean food.)
B) Knowledge of a Fact: 'To know/be aware that something will happen'. This usage is about knowing a future fact or assumption. For present or past facts, the form changes to -ㄴ/는 줄 알다.
저는 그가 내일 올 줄 알아요. (I know that he will come tomorrow.)
Context is crucial for distinguishing these two meanings.
Key Differences in Usage:
- For learned skills like driving or swimming, both patterns are often used interchangeably, but -ㄹ 줄 알다 sounds slightly more specific about the skill itself.
- For situations of possibility, permission, or circumstantial ability, you must use -ㄹ 수 있다. Using -ㄹ 줄 알다 would be unnatural. For example, to say "It might rain tomorrow," you must say "내일 비가 올 수 있어요." Saying "내일 비가 올 줄 알아요" means "I know for a fact it will rain tomorrow," which is a different meaning.
Examples (5)
- 저는 운전할 줄 알아요.
I know how to drive.
Word by Word: I driving know how to.
This emphasizes the learned skill of driving. Using '운전할 수 있어요' is also correct but could imply you have the opportunity to drive right now (e.g., you have a car and keys).
- 지금 너무 바빠서 회의에 갈 수 없어요.
I'm so busy right now that I can't go to the meeting.
Word by Word: Now too busy so meeting to go cannot.
This is about possibility, not skill. The situation (being busy) prevents the action. Using '갈 줄 몰라요' would incorrectly imply you don't know the method of getting to the meeting.
- 피아노 칠 수 있어요?
Can you play the piano?
Word by Word: Piano play can you?
In questions about skills, -ㄹ 수 있다 is very common and natural. '피아노 칠 줄 알아요?' is also correct and slightly more direct about asking if they possess the skill.
- 저는 아직 한글을 읽을 줄 몰라요.
I don't know how to read Hangul yet.
Word by Word: I yet Hangul read how to don't know.
This clearly states a lack of a learned skill. '읽을 수 없어요' could also be used, but might imply a temporary inability (e.g., 'my eyes hurt so I can't read').
- 이 문제는 너무 어려워서 풀 수 없어요.
This problem is too difficult, so I can't solve it.
Word by Word: This problem too difficult so solve cannot.
This expresses an inability due to the circumstances (the problem's difficulty). It's not about lacking the general knowledge of how to solve problems.
Common Mistakes
Using -ㄹ 줄 알다 for possibility.
Different Meaning내일 눈이 올 줄 알아요.Better내일 눈이 올 수 있어요.To express possibility like 'It might snow tomorrow,' you must use -ㄹ 수 있다. The incorrect sentence,
내일 눈이 올 줄 알아요, means 'I know that it will snow tomorrow.' This is a statement about one's knowledge of a fact, not about possibility.Using -ㄹ 줄 모르다 when inability is due to a situation, not lack of skill.
Not Quite목이 아파서 노래를 부를 줄 몰라요.Better목이 아파서 노래를 부를 수 없어요.The reason for not singing is a sore throat (a temporary condition), not a lack of knowing how to sing. Therefore, -ㄹ 수 없다 is the correct choice to express this circumstantial inability.
Related Patterns
- -(으)ㄹ 수 있다/없다Can/cannot
This is one half of the comparison, used for general ability, possibility, and permission. It's the broader and more common way to say 'can/cannot'.
- -ㄴ/는/ㄹ 줄 알다Know How to, Be Aware That
This pattern expresses knowledge. With
-ㄹ, it can mean 'know how to' (a skill) or 'know that something will happen' (a future fact). With-ㄴ/는, it's used for knowing a present fact or state. This lesson focuses on the 'know how to' meaning in contrast with-ㄹ 수 있다. - -ㄴ/는/ㄹ 줄 알았다I Thought That…, I Assumed That…
This pattern looks very similar but has a completely different meaning: 'I thought that...' or 'I assumed that...'. Confusing this with '-ㄹ 줄 알다' is a very common mistake.
- 안/못Not
A related way to express inability. '못 + Verb' is often a shorter, more common way to say 'Verb + -ㄹ 수 없다', especially when the inability is due to lack of skill or external factors.
- -아/어도 되다May, Be Allowed to
This pattern relates to the 'permission' aspect of -ㄹ 수 있다. While you can use -ㄹ 수 있다 to ask for or grant permission, -아/어도 되다 ('may', 'it is okay to') is a more direct and explicit way to do so.