을/ㄹ 수 있다

The Korean grammar pattern 을/ㄹ 수 있다 is one of the most fundamental and versatile structures you will encounter in the Korean language. At its core, it expresses the concept of possibility or capability, equivalent to the English words 'can,' 'be able to,' or 'it is possible to.' Understanding this pattern is crucial because it allows you to describe your skills, ask for permissions, or discuss the likelihood of future events. The word '수' (su) is a bound noun that historically refers to a 'way,' 'method,' or 'possibility.' When combined with the descriptive future participle '을/ㄹ' and the existential verb '있다' (to exist), the phrase literally translates to 'the possibility/way exists' to perform a specific action.

Capability (Ability)

This usage describes a person's physical or mental ability to do something. For example, 'I can swim' or 'I can speak Korean.' It focuses on whether the subject possesses the necessary skills or physical strength to execute the verb.

Possibility (Circumstance)

This usage describes whether a situation allows for an action to occur. Even if you have the skill, the circumstances might dictate if you 'can' do it. For example, 'I can't go to the party because I have work' implies a lack of possibility due to external factors rather than a lack of walking ability.

In daily life, Koreans use this pattern constantly. Whether you are at a restaurant asking if you can pay by credit card, at a job interview discussing your qualifications, or simply chatting with friends about weekend plans, this structure is indispensable. It bridges the gap between simple actions and the potential for those actions. It is also the foundation for its negative counterpart, 을/ㄹ 수 없다, which means 'cannot' or 'to be unable to.' Mastery of this pattern marks the transition from basic survival Korean to more nuanced and expressive communication.

Furthermore, the nuance of 을/ㄹ 수 있다 can change depending on the context. While it often denotes a factual ability, in certain contexts, it can sound like a polite suggestion or a tentative prediction. For instance, when a doctor says '회복할 수 있습니다' (You can recover), it carries the weight of a professional assessment of possibility. In contrast, a friend saying '그럴 수 있어' (That can happen / That's possible) is often used as a comforting phrase to validate someone's feelings or a strange situation.

Permission

While '해도 되다' is more common for 'may I', '을/ㄹ 수 있다' is frequently used to ask if an action is feasible within the rules of a setting. '여기 주차할 수 있나요?' (Can I park here? / Is parking possible here?)

To use 을/ㄹ 수 있다, you must first identify the verb stem. The choice between '을' and 'ㄹ' 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 smoother and more natural for the speaker.

Rule 1: Vowel Stems

If the verb stem ends in a vowel, you attach 'ㄹ 수 있다' directly to the bottom of the stem. For example, the verb '가다' (to go) has the stem '가'. Since '가' ends in the vowel 'ㅏ', it becomes '갈 수 있다'. Similarly, '보다' (to see) becomes '볼 수 있다'.

Rule 2: Consonant Stems

If the verb stem ends in a consonant (batchim), you add '을 수 있다' after the stem. For example, '먹다' (to eat) has the stem '먹'. Since it ends in the consonant 'ㄱ', it becomes '먹을 수 있다'. '읽다' (to read) becomes '읽을 수 있다'.

Irregular verbs require special attention. If a verb stem ends in 'ㄹ', such as '만들다' (to make), you do not add another 'ㄹ'. Instead, you treat it as if the 'ㄹ' is already there and just add '수 있다', resulting in '만들 수 있다'. For 'ㄷ' irregulars like '듣다' (to listen), the 'ㄷ' changes to 'ㄹ' before adding '을', resulting in '들을 수 있다'. For 'ㅂ' irregulars like '돕다' (to help), the 'ㅂ' changes to '우', resulting in '도울 수 있다'.

Tense and formality are applied to the final verb '있다'. You can conjugate it into the present (있어요 / 있습니다), past (있었어요 / 있었습니다), or even future (있을 거예요). For example, '할 수 있었어요' means 'I was able to do it.' To make it negative, simply replace '있다' with '없다' (to not exist), creating '을/ㄹ 수 없다'. This is the standard way to say 'cannot' in a formal or objective manner, though '못' is often used in more casual, subjective contexts.

Honorifics

When speaking to someone highly respected, you can use the honorific version: '을/ㄹ 수 있으시다'. However, it is more common to apply the honorific to the main verb stem if applicable, e.g., '하실 수 있어요' (You [honored] can do it).

In South Korea, 을/ㄹ 수 있다 is ubiquitous, appearing in everything from K-dramas and pop songs to formal news broadcasts and professional workplace settings. Its usage varies slightly across these contexts, reflecting the social hierarchy and the relationship between speakers. In a professional environment, you will often hear '할 수 있습니다' (I can do it) as a standard expression of confidence and capability. Employees use it to assure their managers that they can complete a task or meet a deadline.

In casual social settings, the pattern is frequently used to discuss plans or shared abilities. You might hear friends asking '내일 만날 수 있어?' (Can we meet tomorrow?) or '수영 할 수 있어?' (Can you swim?). In these cases, the '있다' is conjugated to the informal-polite '-어요' or the informal-casual '-어' style. It's also a staple in the service industry. Clerks will tell you '여기서 결제하실 수 있어요' (You can pay here) or '이 옷은 세탁하실 수 없어요' (You cannot wash this clothing item).

In Korean media, particularly variety shows and interviews, celebrities often use this pattern to express their willingness to try new things or to describe their hidden talents. In lyrics, it often takes a more poetic or emotional tone, expressing the possibility of love or the pain of not being able to forget someone ('잊을 수 없어요' - I cannot forget you). In news reports, it is used to state objective possibilities or legal permissions, such as '오늘부터 신청할 수 있습니다' (You can apply starting from today).

Public Announcements

On subways or buses, you might hear '이번 역에서 갈아타실 수 있습니다' (You can transfer at this station). This uses the honorific form to address the public politely.

Advertising

Ads frequently use this to highlight product benefits: '피부를 맑게 할 수 있습니다' (It can make your skin clear).

One of the most frequent mistakes English speakers make when learning 을/ㄹ 수 있다 is confusing it with -ㄹ 줄 알다. While both can be translated as 'can' in English, they have distinct meanings in Korean. '-ㄹ 줄 알다' specifically refers to knowing the *method* or having the *learned skill* to do something. For example, '운전할 줄 알아요' means 'I know how to drive (I have the license and skill).' In contrast, '운전할 수 있어요' could mean the same, but it could also mean 'I am able to drive (right now, because I'm not tired or drunk).' If you use '수 있다' when you specifically mean 'know how to,' it's not wrong, but '줄 알다' is often more precise for acquired skills like languages, cooking, or sports.

Another common error is forgetting the space between the participle and '수'. As mentioned before, '수' is a noun. Therefore, '갈수있다' is a spelling mistake; it must be '갈 수 있다'. Additionally, students often struggle with the 'ㄹ' irregulars. Remember that if a stem ends in 'ㄹ', you don't add another 'ㄹ'. So, '만들다' becomes '만들 수 있다', NOT '만들을 수 있다' or '만들ㄹ 수 있다'.

A subtle mistake involves using this pattern with adjectives to mean 'It can be [adjective].' In English, we say 'It can be cold in the morning.' In Korean, using '추울 수 있다' is possible, but it specifically means 'There is a possibility of it being cold.' Beginners often over-apply this to all adjectives where a different structure like '-아/어질 수 있다' (can become) or '-을 수도 있다' (might) would be more natural. Lastly, ensure you don't confuse '있다' (to exist) with '이다' (to be). It is never '을/ㄹ 수 이다'.

The 'ㄹ' Deletion Error

For stems ending in 'ㄹ', like '살다' (to live), learners often try to add '을', making '살을 수 있다'. Correct: '살 수 있다'.

Confusing Possibility with Permission

While '수 있다' can ask for permission, using '-아/어도 되다' is often more natural for 'May I...?' scenarios. '먹을 수 있어요?' (Can I eat this? / Is it edible?) vs '먹어도 돼요?' (May I eat this?).

To sound more like a native speaker, it is helpful to know the alternatives to 을/ㄹ 수 있다 and when to use them. The most common alternative is 못. While '을/ㄹ 수 없다' is the direct negative of '을/ㄹ 수 있다', '못' is more common in spoken Korean for personal inability. For example, '못 가요' is more natural than '갈 수 없어요' when telling a friend you can't make it to dinner.

-ㄹ 줄 알다 vs. -ㄹ 수 있다

-ㄹ 줄 알다 focuses on 'knowing how' (skill). -ㄹ 수 있다 focuses on 'being able' (possibility/ability). Use '줄 알다' for things you learned like '운전' (driving) or '외국어' (foreign languages).

-기 가능하다 vs. -ㄹ 수 있다

-기 가능하다 (to be possible) is very formal and often used in technical or bureaucratic contexts. '사용이 가능합니다' (Usage is possible) is seen on signs or in manuals, whereas '사용할 수 있습니다' is more general.

Another nuance is -을 수도 있다. By adding the particle '도' (also/even), you shift the meaning from a general 'can' to 'might' or 'could potentially.' This is used when you are less certain about the possibility. For example, '비가 올 수도 있어요' means 'It *might* rain,' whereas '비가 올 수 있어요' is a more direct statement of the possibility. In very formal settings or writing, you might also see -ㄹ 능력이 있다 (to have the ability to), but this is quite rare in daily conversation.

Lastly, for permission, -아/어도 되다 is the standard 'may I' or 'it is okay to.' While you can ask '여기 앉을 수 있어요?' (Can I sit here?), '여기 앉아도 돼요?' is generally perceived as more polite because it asks for the listener's consent rather than just checking the physical possibility of sitting.