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Lesson 2. How to say, “I can” and “I can’t”

There are 2 main ways you can express your ability/inability to do something in Korean:

1. VERB STEM + ㄹ/을 수 있어요/없어요
2. 못 + VERB, VERB STEM + 지 못해요 [못 (adv.) = can’t]

3. VERB STEM + ㄹ/을 줄 알아요/몰라요

These constructions can be used to mean “I can” or “I can’t”; however they can indicate slightly different things.

1. VERB STEM + ㄹ/있다/없다


When using this construction, you imply your ability to do something is either physically, legally or circumstantially possible/impossible.
(It is also sometimes used when talking about your proficiency/skill in something (e.g. I can speak Korean 한국어를 할 수 있어요, I can’t play flute etc 플룻을 불 수 없어요,) but it is still unclear as to whether that’s grammatically correct. But one thing for sure is that there are more natural sounding patterns to talk about your proficiency/skill (or lack thereof), which we’ll learn in this lesson.)

The construction is used as follows:

 I canI can NOT
With 받침Verb stem + 을 수 있다Verb stem + 을 수 없다
Without 받침Verb stem + ㄹ 수 있다Verb stem + ㄹ 수 없다

can be conjugated into different tenses as necessary


I can eat slowly because I’m not late – 안 늦어서 천천히 먹을 수 있어요.

I got my driver’s license yesterday. I can drive now. – 어제 운전 면허를 땄어요. 이제 운전할 수 있어요 (=운전을 할 수 있어요)

I can’t do everything for you – 제가 모두 다 해줄 수가 없어요.*

I was too busy watching the kids, so I couldn’t cook. – 저는 아이들 보느라 바빠서 요리를 할 수 없었어요.

*It is also possible to see the 이/가 particle added to form 수 있다/없다 which has the same meaning but adds a slight emphasis. It can be thought of as saying “I can’t even…”.

Much like this, the 은/는 particle can be added to imply a contrast, forming 수는 있다/없다. For example, 여기에서 잘 수 없어요 – I can’t sleep here (but I may be able to sleep somewhere else, or I may be able to do other things here than sleep).


2. 못 + VERB, VERB STEM + 지 못하다

There’s another construction you can use when expressing you CANNOT do something or something’s not possible :

못 + VERB (more common)

or, VERB STEM + 지 못하다 (slightly more formal)

→ These are interchangeable

Verb-ㄹ/을 수 없다 can be replaced with 못+verb and it will still mean the same thing; in other words, Verb+ㄹ/을 수 없다 and 못+Verb does not have a very significant difference.

However, when talking about your lack of skill or proficiency in something, 못+verb sounds more natural.

This is because 못+verb implies that you are unable to do something for a wider variety of reasons, including the lack of skill or proficiency, physicality or circumstances.  

*TIP: When you are in doubt whether to use -ㄹ/을 수 없어요 or 못+verb / verb+지 못해요, you can go with 못+verb / verb+지 못해요 and it will sound natural most of the time. 



수영할 수 없어요 – I can’t swim (because I physically can’t).
= 수영하지 못해요 / 수영 못해요* – I can’t swim (it could be either I physically can’t or I don’t want my hair to get wet etc.)
*Note: When 못 is combined with 하다 to mean lack of skill, it has to be attached (못하다(O) – without space in between.) However, when 못 is combined with other verbs to mean lack of skill, they have to be spaced. 

피아노를 못 쳐요 – I can’t play piano (because I lack the skill, It’s late at night, I should not disrupt my neighbor etc.)

볼 수 없어요 – I can’t see (because sth isn’t there anymore).
vs. 보지 못해요 / 못 봐요 – I can’t see (because someone’s head is in the way, because I’m not allowed to, because I’m short-sighted etc)

Note: In Korean, it is more common to use the verb 보이다 (to be seen/visible) when saying if you can/cannot see something. The same idea is seen for the verb 들리다 (to be heard/audible).

e.g., 나 보여? – Can you see me? (/am I visible?).

         안 보여 – No I can’t see. 

        제 목소리가 들리시나요? – Can you hear me? (/is my voice audible?)

자가 격리 중이라서 못 나가요. I can’t go out because I am in quarantine. 


2. VERB STEM + ㄹ/알아요/몰라요


This construction can also indicate your ability/skill to do something but it is slightly different to-ㄹ/을 수 있다/없다 since it is closer to implying whether you have LEARNT how to do something or not. For example, in English, this would be the difference between saying “I cannot drive” and “I know how to drive”. This is why 알다 (to know) and 모르다 (to not know) are seen in these constructions. However, because this can still indicate your ability, it is commonly also translated as, “I can” and “I cannot”.

The construction is used as follows:

 I know how toI do NOT know how to
With 받침Verb stem + 을 줄 알다Verb stem + 을 줄 모르다
Without 받침Verb stem + ㄹ 줄 알다Verb stem + ㄹ 줄 모르다

can be conjugated into different tenses as necessary


I know how to compliment in Korean – 저는 한국말로 칭찬할 줄 알아요. (칭찬하다: to compliment)

I don’t know how to make kimchi fried rice – 저는 김치볶음밥을 만들 줄 몰라요.

Can you speak English? – 영어를 할 줄 아세요?

Do you know how to open the water bottle? – 물 병을 열 줄 알아?

I can drive. – 운전할 줄 알아요.



Irregular forms to note

  1. When irregular verbs with ㄷ 받침 are combined with these constructions, the ㄷ becomes a ㄹ to help with pronunciation.

듣다 → 들을 수 있어요 – I can hear.

  1. When verbs with ㄹ 받침 are combined with these constructions, no extra ㄹ or 을 needs to be added.

울다 → 울 수 없어요 – I can’t cry

만들다 → 만들 줄 알다 – I know how to make

  1. When irregular verbs with ㅅ 받침 are combined with these constructions, the ㅅ 받침 is removed before the 을 is added.

낫다 → 감기가 나을 수 있어요 – Your cold can get better

  1. When irregular verbs with ㅂ 받침 are combined with these constructions, the verb stem loses its ㅂ and has a 우 added before it is combined with the construction.

무섭다(to be scary) → 무서울 수 없어요 – It can’t be scary.


Summary and example of the key differences

I can Verb stem + ㄹ/을 수있다Physical/circumstantial ability수영할 수 있어요I can swim (because I am physical able to swim)
 Verb stem + ㄹ/을 줄알다Indicates you have learnt how to do something수영할 줄 알아요I know how to swim (because I was taught when I was younger)
I can not Verb stem + ㄹ/을 수없다Physical/circumstantial inability수영할 수 없어요I cannot swim (because I’ve broken my arm)
 못 + verb / verb stem + 지 못하다Inability due to a variety of possibilities (not much difference from -ㄹ/을 수 없다 and often interchangeable, except when expressing lack of skills)수영하지 못해요 /수영 못해요I can’t swim (because I don’t want to get my hair wet, I lack the skill etc.)
 Verb stem + 줄 모르다Indicates you have not learnt how to do something수영할 줄 몰라요I do not know how to swim (because I was never taught)