(으)ㄹ 수 있다/없다 (can/cannot, able to)

This grammar attaches directly to the stem of a verb. It is a compound structure. The first part is the -(으)ㄹ suffix. This suffix usually points toward the future or a possibility. The second part is 수, which means "way," "method," or "possibility." Finally, we add 있다 (to have/exist) or 없다 (to not have/not exist). When you put them together, you are literally saying "The possibility of [doing something] exists." It sounds a bit formal when translated literally. But in real life, it is very natural and conversational. You will use it to express your skills. You will also use it to talk about your schedule. It is like a grammar traffic light. Green light means 있다 (can). Red light means 없다 (cannot). Most of the time, we use this with verbs. You won't see it with adjectives very often, but there are some exceptions for possibility. Stick to verbs for now to stay safe.

1. 1Building this rule is like playing with Lego blocks. You just need to look at the end of your verb stem.
2. 2If the verb stem ends in a vowel, add -ㄹ 수 있다/없다.
3. 3가다 (to go) becomes 갈 수 있다 (can go).
4. 4보다 (to see) becomes 볼 수 있다 (can see).
5. 5If the verb stem ends in a consonant (받침), add -을 수 있다/없다.
6. 6먹다 (to eat) becomes 먹을 수 있다 (can eat).
7. 7읽다 (to read) becomes 읽을 수 있다 (can read).
8. 8If the verb stem already ends in ㄹ, just add 수 있다/없다. Don't double up the ㄹ!
9. 9만들다 (to make) becomes 만들 수 있다 (can make).
10. 10살다 (to live) becomes 살 수 있다 (can live).
11. 11Watch out for irregular verbs!
12. 12For ㄷ irregulars like 듣다 (to listen), the ㄷ changes to ㄹ. It becomes 들을 수 있다.
13. 13For ㅂ irregulars like 돕다 (to help), the ㅂ changes to 우. It becomes 도울 수 있다.

You can use this pattern in two main ways. First, use it for ability. This is about your personal skills. Can you swim? Can you cook? Can you speak Korean? Use 수 있다 to show off your talents.

• 저는 수영할 수 있어요. (I can swim.)
• 한국말을 할 수 있어요. (I can speak Korean.)

Second, use it for possibility or situation. This is about whether the world allows you to do something. Even if you know how to drive, you "cannot" drive if you don't have a car today.

• 오늘은 바빠서 만날 수 없어요. (I am busy today, so I can't meet you.)
• 여기서 사진을 찍을 수 있어요? (Can I take a photo here?)

It is great for ordering food! "Can you give me more water?" or "Can you make it less salty?" These are perfect times for 수 있다. It makes you sound polite and clear. You'll also use it a lot when making plans. "Can we meet at 5?" "I can go there by bus." It is very versatile.

Even though it means "can," it doesn't always fit every "can" situation. If you are asking for permission, Koreans often use -아/어도 되다 instead. It sounds a bit more natural. For example, "Can I go to the bathroom?" is usually 화장실에 가도 돼요? rather than 갈 수 있어요?. Using 수 있다 there sounds like you are asking if you are physically capable of walking to the bathroom. Awkward!

Also, don't use it for things that are just habits or will. If you simply "don't" eat meat because you're a vegetarian, use the 안 negative or -지 않다. If you say 고기를 먹을 수 없어요, people might think you have a medical allergy or no teeth! Yes, even native speakers get a bit confused if you use the wrong "cannot." Use 수 없다 when there is a real barrier, not just a preference.

The biggest trap is the space. In Korean, 수 is a dependent noun. This means it needs a space before it.

• Wrong: 할수있다
• Right: 할 수 있다

If you forget the space, your Korean friends will still understand you. But your teacher might cry a little bit.

Another mistake is with ㄹ irregulars. Beginners often try to add 을 to 만들다.

• Wrong: 만들을 수 있다
• Right: 만들 수 있다

Just let the existing ㄹ do the work!

Also, don't mix up 못 and 수 없다. 못 usually implies you want to do it but can't. 수 없다 is a bit more objective. However, they are often used interchangeably in casual speech. Just remember that 수 없다 sounds a tiny bit more formal and descriptive.

You might have heard of -(으)ㄹ 줄 알다. This also translates to "can" or "know how to." So what's the difference?

-(으)ㄹ 줄 알다 is strictly about learned skills. Use it for things you had to study or practice, like playing the piano or coding.

-(으)ㄹ 수 있다 is the big umbrella. It covers learned skills AND situational possibility.

Example: If you say 운전할 줄 알아요, it means you have a license and know how to drive. If you say 운전할 수 있어요, it could mean you know how to drive, OR it could mean you are sober enough to drive right now.

Think of 줄 알다 as "I have the knowledge" and 수 있다 as "It is possible for me."