을/를 수 있다

The grammatical structure -(으)ㄹ 수 있다 is the cornerstone of expressing ability and possibility in the Korean language. While English speakers typically use the modal verb 'can' or the phrase 'be able to,' Korean utilizes a combination of a future-prospective modifier and a dependent noun. The word '수' (su) in this context is a dependent noun that historically refers to a 'way,' 'method,' or 'means.' Therefore, when you say you 'can' do something in Korean, you are literally stating that the 'way or possibility to do it exists.'

Core Meaning

Expressing the physical or mental ability to perform an action, or the external possibility of an event occurring.

Usage Context

Used in everyday conversations, formal presentations, and written texts to describe skills, potential outcomes, and permissions.

In Korean society, expressing what one can or cannot do is often tied to social hierarchy and politeness. While the basic meaning remains 'can,' the nuance shifts based on the verb it attaches to and the social context. For instance, stating your ability to speak a language is a common use, but the same structure can be used to politely ask if a certain outcome is possible, such as 'Can I sit here?' or 'Is it possible to finish this by tomorrow?'

The versatility of this structure is immense. It isn't just about 'I have the skill'; it's about the existence of opportunity. If the weather is clear, you 'can' see the mountains; if you have money, you 'can' buy the car. This distinction between internal ability and external possibility is vital for B1 learners to master. Unlike some languages that separate these concepts with different verbs, Korean unifies them under this single, elegant construction.

Furthermore, this expression is frequently paired with various honorifics. When speaking to a superior, '있다' changes to '있습니다' or '있어요,' and in very formal settings or when referring to the subject's ability with high respect, it can even become '-(으)ㄹ 수 있으십니다.' Understanding these layers of formality is what elevates a learner from basic communication to natural, culturally-aware fluency.

In the example above, the focus isn't on the rain's 'skill' to fall, but the 'possibility' of the event. This dual-purpose nature is why you will hear this phrase dozens of times a day in Korea, from weather reports to job interviews. It is perhaps the most functional grammar point in the entire language for expressing potentiality and agency.

Using -(으)ㄹ 수 있다 correctly requires a basic understanding of Korean verb stems and the rules for attaching suffixes. The construction depends entirely on whether the verb stem ends in a vowel or a consonant. This is a standard phonological rule in Korean designed to make the transition between sounds smooth and natural.

Rule 1: Vowel Stems

If the verb stem ends in a vowel, attach '-ㄹ 수 있다'. Example: 가다 (to go) becomes 갈 수 있다.

Rule 2: Consonant Stems

If the verb stem ends in a consonant (batchim), attach '-을 수 있다'. Example: 먹다 (to eat) becomes 먹을 수 있다.

Rule 3: 'ㄹ' Batchim

If the stem already ends in 'ㄹ', just add '수 있다'. Example: 만들다 (to make) becomes 만들 수 있다.

One of the most important aspects for intermediate learners is the tense of the sentence. While '-(으)ㄹ 수 있다' is the base form, you can change the tense by conjugating the final verb '있다'. To say 'could' or 'was able to,' you change '있다' to '있었다'. For example, '저는 어제 그 책을 읽을 수 있었어요' (I was able to read that book yesterday). Conversely, to express future possibility, you can say '-(으)ㄹ 수 있을 거예요'.

Negation is another crucial component. There are two ways to say you 'cannot' do something. The first is replacing '있다' (to exist/to have) with '없다' (to not exist/to not have), resulting in '-(으)ㄹ 수 없다'. This often sounds more formal or absolute. The second way is using the short negation '못' before the verb, like '못 가요' (I can't go). While both mean 'cannot,' '-(으)ㄹ 수 없다' emphasizes the lack of possibility or method more strongly.

When constructing complex sentences, you can also add adverbs like '잘' (well) to indicate proficiency. '한국어를 잘 할 수 있어요' means 'I can speak Korean well.' If you want to ask for a favor, you might use the question form: '도와줄 수 있어요?' (Can you help me?). This is slightly more direct than the '-(으)ㄹ 수 있을까요?' form, which is used to be extra polite and tentative.

Mastering the conjugation rules is just the first step; the second is knowing how to balance the formality levels. Using '-(으)ㄹ 수 있나요?' is a common polite question form in service industries, while '-(으)ㄹ 수 있어' is reserved for close friends. By practicing these variations, you ensure that your Korean sounds natural and appropriate for any social setting you encounter.

In the bustling streets of Seoul or within the quiet confines of a Korean office, -(으)ㄹ 수 있다 is omnipresent. It is the language of capability, negotiation, and prediction. You will hear it in subway announcements, variety shows, K-dramas, and corporate boardrooms. Its frequency is so high because it covers both the 'can' of ability and the 'might' of possibility, making it indispensable for any communicative task.

Public Announcements

'이번 역에서 갈아타실 수 있습니다' (You can transfer at this station). This is a standard phrase heard on every subway line in Korea.

Workplace & Business

'오늘까지 제출할 수 있습니까?' (Can you submit it by today?). Managers use this to check feasibility and deadlines.

In popular culture, particularly K-Dramas, this structure is often used to express emotional possibility or resolve. A character might say '나는 너를 잊을 수 없어' (I can't forget you), where the 'cannot' indicates an emotional impossibility rather than a lack of skill. This emotional weight shows how the grammar transcends simple 'can' and enters the realm of deep personal expression.

The phrase '할 수 있다' has even become a national mantra of sorts. During the 2016 Rio Olympics, Korean fencer Park Sang-young was seen muttering '할 수 있다, 할 수 있다' to himself while trailing in a match, eventually coming back to win the gold. This moment solidified the phrase as a symbol of the 'can-do' spirit and resilience in Korean culture. You will see it on motivational posters and hear it from coaches and teachers across the country.

In restaurants, you'll use it to ask about menu modifications: '포장할 수 있어요?' (Can I get this to go?). In stores: '입어 볼 수 있어요?' (Can I try this on?). It is the primary tool for navigating the world of Korean services. Because Korean culture values politeness, using the '-ㄹ 수 있을까요?' (Could it be possible...?) form in these situations will make you sound much more sophisticated and respectful to the staff.

Finally, in academic or news contexts, the structure is used to discuss probabilities and scientific possibilities. '이 약은 부작용이 있을 수 있습니다' (This medicine may have side effects). Here, the focus is entirely on objective possibility. Whether you are reading a scientific paper or a celebrity gossip column, '-(으)ㄹ 수 있다' provides the necessary framework to discuss what is possible in our world.

While -(으)ㄹ 수 있다 is straightforward in its basic form, learners frequently encounter pitfalls when it comes to nuance, irregular verbs, and overlapping grammar points. Avoiding these common errors will significantly improve your fluency and make your Korean sound more natural.

Mistake 1: Confusion with -(으)ㄹ 줄 알다

Learners often use '-(으)ㄹ 수 있다' for skills they have learned, like swimming or driving. While not wrong, '-(으)ㄹ 줄 알다' specifically means 'to know how to.' If you say '수영할 수 있어요,' it could mean 'I have the skill' OR 'I am allowed to swim here.' '수영할 줄 알아요' strictly means 'I know how to swim.'

Mistake 2: Irregular Verb Conjugation

Verbs ending in 'ㄷ', 'ㅂ', or 'ㅅ' often change. For example, '듣다' (to listen) becomes '들을 수 있다' (not 듣을 수 있다). '돕다' (to help) becomes '도울 수 있다'. Forgetting these changes is a very common error for B1 students.

Another frequent mistake is the over-reliance on this structure for 'permission.' In English, we say 'Can I go to the bathroom?' In Korean, while '갈 수 있어요?' is understandable, it sounds a bit like you're asking about your physical ability to walk there. For permission, it is often more natural to use '-아/어도 되다' (Is it okay if...?). For example, '화장실에 가도 돼요?' is the standard way to ask for permission, whereas '갈 수 있어요?' might be interpreted as 'Is the path to the bathroom clear?'

A subtle mistake involves the use of '있다' versus '없다' in negative questions. In English, 'Can't you do it?' is a common question. In Korean, '할 수 없어요?' sounds very heavy and dramatic. Usually, people use '못 해요?' or '할 수 없나요?' to be more natural. Additionally, learners sometimes forget to add the '을' or 'ㄹ' altogether, saying '가 수 있다' instead of '갈 수 있다'. The modifier is essential because '수' is a noun that needs a modifier to make sense.

Lastly, be careful with the word order when using negations like '안' or '못'. You should not say '안 할 수 있다' to mean 'cannot do.' You must use '할 수 없다' or '못 하다'. Saying '안 할 수 있다' actually means 'It is possible to NOT do it,' which is a completely different meaning! Mastering these distinctions is what separates a proficient speaker from a perpetual student.

By paying attention to these nuances—especially the difference between 'ability' and 'permission' and the specific conjugation of irregular stems—you will avoid the most common traps that catch English speakers learning Korean.

While -(으)ㄹ 수 있다 is the most common way to express 'can,' Korean offers several alternatives that provide more specific nuances. Choosing the right one depends on whether you are talking about a learned skill, a physical impossibility, or a formal permission.

-(으)ㄹ 줄 알다

Used specifically for skills or 'know-how.' Use this for things like 'I know how to cook' (요리할 줄 알아요) or 'I know how to play piano' (피아노를 칠 줄 알아요).

못 (Adverbial Negation)

The most common way to say 'cannot' in daily speech. '못 가요' is more common than '갈 수 없어요' in casual conversation when something prevents you from going.

-기 가능하다 (Possible)

A more formal, Sino-Korean based way to say 'it is possible.' Often used in business or technical writing. '예약이 가능합니다' (Reservation is possible).

Another interesting alternative is '-(으)ㄹ 리가 없다', which means 'There is no way that...' or 'It's impossible that...'. This is used when you are expressing strong disbelief. While '할 수 없다' means you can't do it, '할 리가 없다' means the very idea of it happening is absurd. This is a great structure to add to your B1/B2 repertoire to sound more expressive.

For permission, as mentioned before, '-아/어도 되다' is the superior choice. If you want to say 'You can eat this' (meaning 'I give you permission'), '먹어도 돼요' is much more natural than '먹을 수 있어요'. The latter sounds like you are confirming the person has the biological capability to swallow the food, which can sound unintentionally funny or sarcastic in the wrong context.

Finally, there is the structure '-(으)ㄹ 수밖에 없다', which means 'to have no choice but to...' or 'cannot help but...'. It literally translates to 'there is no way other than...'. This is a very common idiomatic use of the '수' noun. For example, '비가 오니까 집에 있을 수밖에 없어요' (Since it's raining, I have no choice but to stay home). Understanding these variations allows you to navigate the spectrum of 'can' and 'must' with precision.

By comparing '-(으)ㄹ 수 있다' with these alternatives, you gain a deeper understanding of the Korean logical framework. Each alternative carves out a specific niche of meaning, allowing you to be exactly as polite, certain, or emotional as you intend to be.