Korean Ability Expressions: -을 수 있다/없다

Learn how to express ability and inability in Korean using -을/ㄹ 수 있다 and -을/ㄹ 수 없다, with tables, examples, and common usage tips.

Saying "I can" or "I can't" do something is one of the first practical grammar patterns every Korean learner needs — and it follows one clean, consistent structure across nearly every verb.

The Basic Pattern: -을/ㄹ 수 있다/없다

Attach -을 수 있다 (can) or -을 수 없다 (cannot) to a verb stem, choosing -을 or -ㄹ depending on whether the stem ends in a consonant or vowel.

Stem ends in	Can	Cannot
Consonant	-을 수 있어요	-을 수 없어요
Vowel	-ㄹ 수 있어요	-ㄹ 수 없어요

Examples:

• 저는 한국어를 할 수 있어요. — I can speak Korean.
• 저는 매운 음식을 먹을 수 없어요. — I can't eat spicy food.
• 그는 피아노를 칠 수 있어요. — He can play the piano.

Asking About Ability

• 수영할 수 있어요? — Can you swim?
• 이거 오늘까지 끝낼 수 있어요? — Can you finish this by today?

-을 줄 알다/모르다: Learned Skill vs General Ability

A related but distinct pattern, -을 줄 알다 (know how to) and -을 줄 모르다 (don't know how to), specifically emphasizes a learned skill rather than general possibility.

Pattern	Meaning
운전할 줄 알아요.	I know how to drive. (learned skill)
운전할 수 있어요.	I can drive. (ability, possibly circumstantial)

In many everyday contexts these overlap, but -을 줄 알다 specifically highlights that you learned the skill, while -을 수 있다 is broader and can include temporary circumstances too (예: 오늘은 차가 있어서 갈 수 있어요 — I can go today because I have a car).

Common Mistakes to Avoid

1. Forgetting the consonant/vowel rule. Using -을 with a vowel-ending stem (or vice versa) is one of the most frequent beginner slip-ups.
2. Mixing up 수 있다 and 줄 알다 carelessly. They are close in meaning but not always interchangeable — 수 있다 is the safer default for general "can" statements.

Quick FAQ

Is there a past tense version? Yes — 할 수 있었어요 (could/was able to) and 할 수 없었어요 (couldn't/was not able to).

How do I say "maybe I can"? Add -을/ㄹ 수도 있어요 (there's also a possibility that...) for a softer, less certain statement of ability or possibility.

Ability expressions unlock so much real conversation — describing skills, negotiating deadlines, talking about hobbies. Klovers' lessons give you practice using this pattern.