안 (An) vs 못 (Mot): Won't vs Can't in Korean Negation

안 negates by choice — 안 먹어요 means "I don't eat it," full stop, no excuse attached. 못 negates by inability — 못 먹어요 means "I can't eat it," something outside your control is stopping you. Both sit directly before the verb, except inside 하다 compounds, where they wedge between the noun and 하다: 공부 안 해요, never 안 공부해요. Formal or written Korean swaps to the longer -지 않다 / -지 못하다 forms instead.

Textbooks teach 안 and 못 in the same lesson, back to back, like they're interchangeable flavors of "no." They're not. 안 is about willpower — you're choosing not to. 못 is about circumstance — something is stopping you whether you like it or not. Mix them up and you don't just sound slightly off, you accidentally confess to something. Say 저 안 가요 ("I'm not going, my choice") when you mean 저 못 가요 ("I can't go, sadly"), and you've turned a polite decline into a flat refusal.

The good news: once the choice-vs-inability split clicks, the rest is mechanical. Here's the whole system, including the one placement rule that trips up nearly everyone learning this.

The clean split: 안 chooses, 못 can't

안 goes in front of a verb to say you're simply not doing it. No reason required, none implied. 못 goes in front of a verb to say you're physically, situationally, or skill-wise unable to do it. Same verb, same slot, opposite story.

One shortcut that actually works: if you could finish the sentence with "...because I don't want to," reach for 안. If you'd finish it with "...even though I want to," reach for 못. Native speakers make this call instantly and so will you, once you've said it wrong in front of someone a couple of times.

Where 안 and 못 actually sit in the sentence

For a plain verb, both particles land right before it — 안 가요, 못 가요, 안 먹어요, 못 먹어요. Simple. The trap is 하다 compound verbs: 공부하다 (to study), 운동하다 (to exercise), 청소하다 (to clean), and roughly half the verbs you'll learn in your first year. With these, 안 and 못 don't go before the whole word. They squeeze in between the noun and 하다.

This is the number one mechanical error with 안/못, and it's not close. English speakers default to putting the negator before the verb because that's what English does — "I don't study" negates "study," not some invisible noun in front of it. Korean's 하다 verbs are secretly two pieces (a noun + "do"), and the negation slots into the seam. Once you notice the seam, you stop making this mistake for good.

The formal cousin: -지 않다 / -지 못하다

안 and 못 are the spoken, everyday forms. Korean also has a longer version built by attaching -지 않다 (for 안) or -지 못하다 (for 못) to the verb stem. Same meaning, different register — think "can't" versus "am unable to." You'll meet these constantly in news articles, essays, and any writing that wants to sound composed rather than conversational.

The short forms aren't "lower level" Korean — dramas, group chats, and daily conversation run on 안/못. But if you're writing a self-introduction essay, a formal email, or anything for a Korean honorifics context, -지 않다/-지 못하다 is the safer, more polished choice. Learn to recognize both; default to the short form when speaking.

못 가요 is the graceful no

Here's the part textbooks skip entirely: 안 and 못 don't just differ grammatically, they differ socially. Turning down an invitation with 안 가요 ("I'm not going") can land as a flat rejection — you're choosing to skip it, full stop, maybe even skipping them. Turning it down with 못 가요 ("I can't go") shifts the blame onto circumstance instead of onto the relationship. Nobody's feelings get involved; the deadline is the villain, not you.

This is why Koreans reach for 못 constantly in social refusals even when the real reason is closer to "I'd rather not." It's a face-saving move for both sides, and once you start using it that way, your Korean stops sounding like a translated sentence and starts sounding like something a person actually says.

Two verbs that ignore the rule entirely

안/못 attach to almost every action and description verb — except two extremely common ones that already have built-in negative forms and refuse the pattern.

These two are worth memorizing on sight, because they're also two of the most common verbs in the language — you'll use "I don't know" and "I don't have" long before you need most of your other vocabulary. For the full can/can't picture, pair this with ㄹ 수 있다/없다, which covers ability and possibility from the other direction.