지 못하다 (cannot, unable to - formal)

This pattern is what we call "long negation." You attach it to the end of a verb stem. Unlike some grammar rules, this one is very stable. It doesn't care if the verb ends in a vowel or consonant. It just sticks right on there. It specifically shows that an action is impossible. This isn't about choice. It is about ability or external circumstances. If you don't like spicy food, you use a different rule. If you literally can't handle the heat, you use this one. It is like a grammar safety net for your intentions.

1. 1Creating this form is as easy as making instant noodles. Just follow these steps:
2. 2Find the basic form of the verb (the dictionary form).
3. 3Remove the 다 to get the verb stem.
4. 4Add 지 못하다 directly to that stem.
5. 5Let’s look at some quick examples:
6. 6가다 (to go) becomes 가지 못하다.
7. 7먹다 (to eat) becomes 먹지 못하다.
8. 8공부하다 (to study) becomes 공부하지 못하다.
9. 9You can then conjugate the 하다 part for tense or politeness. For example, 가지 못해요 (present polite) or 가지 못했습니다 (past formal). It is that simple! No irregular surprises are hiding here to ruin your day.

Use this when you need to be polite or formal. It is perfect for a job interview. Imagine being asked if you can start tomorrow. If you can't, 지 못하다 sounds much more professional than a blunt 못. Use it when writing emails to your boss or teachers. It is also great for giving specific reasons for your absence.

• "I cannot attend the meeting."
• "I cannot eat peanuts due to allergies."
• "I cannot understand the map."

It feels like a polite bow in sentence form. It shows you tried but faced a wall. Even native speakers prefer this in serious settings.

Don't use this for things you simply choose not to do. If you are lazy and don't clean your room, use 지 않다. Using 지 못하다 there would sound like a ghost is blocking you. Also, be careful with adjectives. This rule is mostly for verbs. You can't usually say a room "cannot be big." That makes no sense! There are tiny exceptions like 편하다 (to be comfortable), but stick to verbs first. Think of it like a "Can't do" sign, not a "Don't like" sign.

The biggest trap is mixing up 지 않다 and 지 못하다. One is "I won't," and the other is "I can't." If you say 공부하지 못해요 during a test, you lack the ability. If you say 공부하지 않아요, you are just choosing to fail. Don't let your teacher get the wrong idea! Another mistake is putting a space between 지 and 못하다. Keep them close! They are best friends. Also, remember to conjugate the final 하다. Leaving it as 지 못하다 in a conversation sounds like a robot reading a manual.

You might know the short version: 못 + Verb. They mean the same thing, but the vibe is different. 못 가요 is fast and casual. 가지 못해요 is elegant and clear. It’s like wearing a tuxedo versus a t-shirt. Both cover your body, but one is for a wedding. There is also ㄹ 수 없다. That one is more about general possibility. 지 못하다 feels a bit more personal or focused on the specific effort. It's the difference between "It's impossible to go" and "I am unable to go."