A2
(으)ㄹ 수 있다 — can
How Korean expresses ability with ㄹ 수 있다, why its negative uses 없다, and how it differs from 못.
ㄹ 수 있다 after a vowel, 을 수 있다 after a consonant. 수 means way, means, so the whole phrase is a way to do it exists.
한국어를 할 수 있어요.
Hangugeoreul hal su isseoyo.
I can speak Korean.
매운 음식을 먹을 수 있어요?
Maeun eumsigeul meogeul su isseoyo?
Can you eat spicy food?
The negative uses 없다
Because the construction is built on 있다, its negative is 없다 — not 안.
할 수 안 있어요.
할 수 없어요.
있다 has its own negative. 안 있다 is not said, here or anywhere.
Against 못
못 and 을 수 없다 overlap, and 못 is shorter and more common in speech. 을 수 없다 is more formal and states an impossibility rather than a personal failure.
오늘은 못 가요.
Oneureun mot gayo.
I can’t go today.
여기서는 담배를 피울 수 없습니다.
Yeogiseoneun dambaereul piul su eopseumnida.
Smoking is not permitted here.
The second is the language of signs. 못 피워요 would sound like the speaker personally lacks the ability.
Also permission
The same form covers may as well as can, and context separates them.
들어갈 수 있어요?
Deureogal su isseoyo?
Can I go in?
For permission specifically, 아/어도 되다 is more precise — see permission.
줄 알다 is a different can
Knowing how to do something — a learned skill — is 을 줄 알다.
수영할 줄 알아요.
Suyeonghal jul arayo.
I know how to swim.