-지 못하다 Cannot: Meaning, Rules and Examples

What you'll learn

• Build -지 못하다 from a verb stem in the polite, past and formal forms.
• Choose between 못, -지 못하다 and -(으)ㄹ 수 없다 for "cannot."
• Put the tense on 못하다 and write it without a space.
• Use -지 못해서 to apologise and -지 못했어요 with 아직 for "not yet."
• Fix the most common mistake: stacking 못 with -지 못하다.

Before you start: you should know the polite ending -아요/-어요 and the difference between "do not" and "cannot." If not, read 안 vs 못 first. Audio plays only when you press a button.

What Does the -지 못하다 Cannot Form Mean?

The -지 못하다 cannot form means "cannot" or "was unable to," and it is the long way to say that something stops you. The short way puts 못 before the verb (못 가요). The long way attaches 지 to the stem and uses the helper verb 못하다. Both ways give the same meaning, and both say that the cause is outside the speaker's will.

A stem (어간, eogan) is the verb with the ending -다 removed. 가다 ("to go") has the stem 가. 끝내다 ("to finish") has the stem 끝내. The helper verb 못하다 carries the tense and the politeness ending, so it conjugates for the whole phrase.

A First Example

Two sentences show the pattern. Each line gives Korean, Revised Romanization (RR, the official Latin spelling, used here only as a learning aid) and the meaning.

• 숙제를 끝내지 못했어요. (sukjereul kkeunnaeji motaesseoyo.) [숙쩨를 끈내지 모태써요] = "I could not finish the homework." The stem 끝내 plus 지 plus 못했어요 (past).
• 기다리지 못해요. (gidariji motaeyo.) [기다리지 모태요] = "I cannot wait." The stem 기다리 plus 지 plus 못해요 (present).

In both sentences the first part stays fixed and 못하다 takes the ending. The next section shows how to build every common form.

How Does the -지 못하다 Cannot Form Work?

The -지 못하다 cannot form works in two steps: attach 지 to the stem, then conjugate 못하다 like any 하다 verb. The first part never changes. Only 못하다 takes different endings.

Step one: stem + 지. Remove 다 from the dictionary form and add 지: 가다 gives 가지, 먹다 gives 먹지, 기다리다 gives 기다리지.

Step two: conjugate 못하다. 못하다 is a 하다 verb, so it follows the 하다 pattern: 못해요 (polite), 못했어요 (past), 못할 거예요 (future), 못합니다 (formal), 못해 (casual).

Write 못하다 as one word. In this pattern 못하다 has no space: 가지 못해요, not 가지 못 해요. The space belongs to the short form, 못 가요, where 못 is a separate adverb.

The conjugator shows the full chain for 가다. Because the first part is fixed, you only need to learn the endings of one helper verb.

Which Forms Does the Pattern Table Show?

The table lists the common forms. Every row uses the same first part, and only 못하다 changes.

The three buttons above play the polite, formal and connecting forms of the table. In sentence form, 먹지 못하고 갔어요 (meokji motago gasseoyo.) [먹찌 모타고 가써요] means "I left without being able to eat." With the forms in view, the rule can be used to build a sentence from scratch.

How Do You Build 숙제를 끝내지 못했어요 Step by Step?

You build a -지 못하다 sentence in five steps: find the dictionary form, remove 다, add 지, conjugate 못하다, and join them. The example below builds "I could not finish the homework."

1. Find the dictionary form. The verb is 끝내다 ("to finish"). The positive sentence is 숙제를 끝냈어요. (sukjereul kkeunnaesseoyo.) = "I finished the homework."
2. Remove 다. The stem is 끝내.
3. Add 지. The connector gives 끝내지.
4. Conjugate 못하다. For the polite past, 못하다 becomes 못했어요.
5. Join and read. 숙제를 끝내지 못했어요. = "I could not finish the homework."

You will know it worked when the object particle 를 stays on 숙제 and only the verb part is rebuilt. The usual slip at this point is putting the past tense on the stem, as in 끝냈지 못해요. The tense goes on 못하다.

Here is the same method with a time word. Add 아직 ("yet") at the front: 아직 끝내지 못했어요. (ajik kkeunnaeji motaesseoyo.) = "I have not been able to finish yet." The skill is identical. The time word only adds when. A different question comes next: how does this form differ from the others that mean "cannot"?

How Is -지 못하다 Different from Similar Forms?

The -지 못하다 cannot form is the long form of 못, and it differs from -(으)ㄹ 수 없다, which says "there is no possibility," and from -지 않다, which says "do not." The table compares them on the same verb.

The first two columns mean the same thing. 못 가요 and 가지 못해요 both say "I cannot go." The pattern -(으)ㄹ 수 없다 is broader. 갈 수 없어요 can say that going is impossible for anyone, for example because a road is closed. For related lessons, see 못 can't in Korean and korean can grammar.

The choice between "do not" and "cannot" is explained in 안 vs 못. The long form of "do not" is in -지 않다 negation. With the comparison clear, the next question is where -지 못하다 is the best choice.

When Do You Use It, and When Not?

Use -지 못하다 in writing, in formal speech and in apologies, and watch for two special meanings. Four cases cover most real needs.

• Apologies and explanations. 가지 못해서 죄송해요. (gaji motaeseo joesonghaeyo.) [가지 모태서 죄송해요] = "I am sorry that I could not go." The pattern -지 못해서 gives the reason politely and is common in messages.
• "Not yet." 아직 끝내지 못했어요 means that the action has not happened so far. The word 아직 pairs naturally with the past form of 못하다.
• Falling short of a standard. With a few adjectives, -지 못하다 means "not as ... as it should be." 건강하지 못해요. (geonganghaji motaeyo.) = "I am not healthy enough" or "Health is not good." This use is formal and soft.
• Formal speech and writing. 가지 못합니다 is the polite formal form used in announcements and letters.

There are also cases where -지 못하다 should not be used. If you simply do not want to go, use -지 않다: 가지 않아요. If you want to say "please do not go," use -지 마세요. For the word 못하다 on its own, a spacing difference carries a meaning difference. 노래를 못해요. (noraereul motaeyo.) [노래를 모태요] says that singing is a weak skill, "I am bad at singing." 노래를 못 해요 says that something stops you from singing now. In speech the two sound the same, so the difference shows only in spelling and in context.

An honest limit: this lesson covers -지 못하다 as a plain negative of inability. It does not cover the fixed patterns built on it, such as -지 못하게 하다 ("to prevent"), and it does not cover the full range of adjectives that accept it. Before moving on, check the mistakes that cost learners the most points.

What Mistakes Do Learners Make?

Learners most often double the inability marker and mis-space 못하다. Five mistakes appear again and again, and each has a quick repair.

1. Stacking 못 with -지 못하다. Learners often assume that adding both is stronger. Actually, it is wrong. Write 못 가요 or 가지 못해요, not 못 가지 못해요.
2. Spacing 못하다 wrongly. Write 가지 못해요, not 가지 못 해요. In the long form, 못하다 is one word.
3. Putting the tense on the stem. Write 가지 못했어요, not 갔지 못해요. The tense marker goes on 못하다.
4. Using it for "do not want to." 가지 못해요 says that something stops you. If you do not want to go, write 가지 않아요.
5. Using it on adjectives in general. Write 예쁘지 않아요 ("is not pretty"), not 예쁘지 못해요. The "not good enough" meaning works only with a few adjectives, such as 건강하다.

A quick self-check: is the first word an action verb stem, is the tense on 못하다, and is there no space inside 못하다? If so, the pattern is right. Practice makes this check automatic.

Practice and Answers

Try the four items before you read the answer key. Cover the answers with your hand.

1. Choose the form. 저는 오늘 가___ 못해요. (지 / 고)
2. Fix the error. 저는 어제 가지 못 했어요. Rewrite it with the correct spacing.
3. Translate. "I am sorry that I could not come." Use -지 못해서.
4. Write your own. Write one sentence with -지 못해요 and an action verb, and one with 아직 and -지 못했어요. Say the English meaning of each.

Answer key

1. 지. The pattern is stem + 지 + 못해요, so the sentence is 저는 오늘 가지 못해요 and means "I cannot go today."
2. 저는 어제 가지 못했어요. In the long form, 못하다 is one word, so there is no space inside 못했어요.
3. 오지 못해서 죄송해요. (oji motaeseo joesonghaeyo.) [오지 모태서 죄송해요] The verb 오다 ("to come") has the stem 오.
4. Answers vary. Check that the first sentence has stem + 지 + 못해요, such as 저는 수영하지 못해요 (I cannot swim). Check that the second has 아직 and the past, such as 아직 읽지 못했어요 (I have not been able to read it yet).

One more rule of thumb: if the English sentence has "cannot" or "was unable to" and the style is formal or written, use -지 못하다. If it is casual speech, use 못.

Next Lessons after the -지 못하다 Cannot Form

After the -지 못하다 cannot form, study the request form, then the wider ability patterns. This lesson teaches one pattern of inability. It does not teach every way to say "cannot" in Korean, which is spread across the negation and ability lessons.

1. Start with -지 마세요 don't, which makes polite requests.
2. Continue with 못 can't in Korean, the short form of this lesson, for spoken Korean.
3. Review -지 않다 negation and 안 vs -지 않다 for the long form of "do not."
4. Return to Korean negation to see every lesson in the set, or open korean can grammar for the positive side of ability.

With these steps, the -지 못하다 cannot form becomes automatic: take the stem, add 지, and conjugate 못하다 for the tense you need.

Frequently Asked Questions

Does -지 못하다 mean the same as 못?

Yes, in meaning. 가지 못해요 and 못 가요 both say "I cannot go." The difference is style: 못 is short and spoken, and -지 못하다 is longer, so it is common in writing and formal speech. Both say that something stops you, not that you choose not to.

Why is 못하다 written without a space here?

In -지 못하다, 못하다 is one helper verb, so it is written together: 가지 못해요. In the short form, 못 is a separate adverb before the verb and has a space: 못 가요. The spaced and unspaced versions also differ in meaning when 못하다 stands alone, as in 노래를 못해요.

Can I use -지 못하다 with adjectives?

Rarely. It mainly goes with action verbs. A few adjectives accept it in the meaning "not as good as it should be": 건강하지 못하다 means "not healthy enough." For a plain negative of an adjective, use 안 or -지 않다: 예쁘지 않아요, not 예쁘지 못해요.

How do I apologise for not being able to come?

Say 가지 못해서 죄송해요, which means "I am sorry that I could not go." The pattern -지 못해서 gives the reason and names the missing action. The form is polite and common in messages. Add 정말 before 죄송해요 to sound more sincere.

Can I say 못 가지 못해요 for emphasis?

No. Use one inability marker only: either 못 가요 or 가지 못해요. Doubling them is wrong. If you want emphasis, add a time or a reason, such as 오늘은 도저히 가지 못해요 ("I truly cannot go today"). The adverb 도저히 adds the strength.