Korean has two short negators that both sit right in front of the verb, and the difference between them is one English blurs constantly. 안 says the action doesn't happen — because you choose not to, or because it simply isn't the case. 못 says the action can't happen — you would if you could, but something blocks you: a lack of ability, a circumstance, a rule. The governing contrast is volition versus impossibility. 안 마셔요 is "I don't drink" (my choice); 못 마셔요 is "I can't drink" (my body won't let me, or I'm not allowed).
English papers over this with context. "I don't drink" can mean either a lifestyle choice or a medical impossibility, and you sort it out from the situation. Korean forces you to commit to one reading right there in the grammar, which is actually a gift: it makes you say exactly what you mean.
안: negation by choice or fact
Put 안 directly before the verb to say the action doesn't occur — whether because you decline it or because the statement is just false.
오늘은 술을 안 마셔요.
oneureun sureul an masyeoyo
I'm not drinking today. (my choice)
저는 고기를 안 먹어요.
jeoneun gogireul an meogeoyo
I don't eat meat. (I choose not to)
안 also negates descriptive verbs (what English calls adjectives) — and here it's the only option, because you cannot be "unable to be" something. A state simply is or isn't the case.
오늘 날씨가 안 추워요.
oneul nalssiga an chuwoyo
The weather isn't cold today.
그 영화는 안 무서워요.
geu yeonghwaneun an museowoyo
That movie isn't scary.
못: negation by inability
Put 못 before the verb to say you can't do the action — you're willing, but blocked. The block can be internal (no skill, no capacity) or external (no time, no ticket, no permission).
오늘은 술을 못 마셔요.
oneureun sureul mot masyeoyo
I can't drink today. (I'm driving / not allowed)
다리를 다쳐서 오늘은 못 뛰어요.
darireul dacheoseo oneureun mot ttwieoyo
I hurt my leg, so I can't run today.
표가 없어서 영화를 못 봤어요.
pyoga eopseoseo yeonghwareul mot bwasseoyo
There were no tickets, so I couldn't see the movie.
Because 못 is fundamentally about capacity, it attaches only to action verbs. It cannot attach to a descriptive verb — there is no such thing as being "unable to be pretty" or "unable to be busy." That restriction is the single hardest edge of the rule, and the mistakes section returns to it.
The minimal pair
Swap only the negator and the meaning turns on a pivot from won't to can't:
| 안 — choice / fact | 못 — inability |
|---|---|
| 술을 안 마셔요 — I don't drink (I choose not to) | 술을 못 마셔요 — I can't drink (no tolerance / forbidden) |
| 안 가요 — I'm not going (don't want to) | 못 가요 — I can't go (something prevents me) |
| 안 잤어요 — I didn't sleep (chose to stay up) | 못 잤어요 — I couldn't sleep (I tried, but couldn't) |
That last row is worth savoring. 안 잤어요 says you deliberately skipped sleep; 못 잤어요 says you lay there wide awake and sleep wouldn't come. Same English "I didn't sleep," two very different nights.
Long forms mirror the short ones
Each short negator has a longer clausal counterpart that attaches to the verb stem with -지. They mean the same thing and swap in for register or rhythm; the long forms feel a touch more deliberate or formal.
- 안 → -지 않다 (negation by choice/fact)
- 못 → -지 못하다 (negation by inability)
저는 담배를 피우지 않아요.
jeoneun dambaereul piuji anayo
I don't smoke. (long form of 안)
무서워서 타지 못해요.
museowoseo taji motaeyo
I'm scared, so I can't ride it. (long form of 못)
Note the pronunciation of 못하다: the ㅅ[t] fuses with the following ㅎ into an aspirated [ㅌ], so 못해요 is said [모태요] and romanized motaeyo — one of the few places 못 changes shape when bound to 하다.
하다-verbs split the negator inside
Verbs built from a noun plus 하다 — 공부하다, 운동하다, 일하다, 요리하다 — behave specially. The negator does not go in front of the whole verb; it slips between the noun and 하다. So "don't study" is 공부 안 해요, and "can't study" is 공부 못 해요.
요즘 바빠서 운동 안 해요.
yojeum bappaseo undong an haeyo
I'm busy these days, so I don't exercise. (choice)
다쳐서 운동 못 해요.
dacheoseo undong mot haeyo
I got hurt, so I can't exercise. (inability)
Putting the negator in front of the whole verb — ×안 운동해요 — is a fossilized beginner error worth stamping out early. The rule is mechanical: find the noun, drop the negator right after it, then 해요.
Common Mistakes
1. Attaching 못 to a descriptive verb. Inability doesn't apply to states. You can't be "unable to be busy" — you either are busy or you aren't, which is 안.
❌ 못 바빠요.
mot bappayo
Wrong — a state can't be 'unable'; use 안.
✅ 안 바빠요.
an bappayo
I'm not busy.
2. Fronting the negator on a 하다-verb. With 공부하다, 운동하다, and friends, the negator goes between the noun and 하다.
❌ 안 공부해요.
an gongbuhaeyo
Wrong word position for a 하다-verb.
✅ 공부 안 해요.
gongbu an haeyo
I don't study.
3. The same fronting error with 못. 못 splits the 하다-verb exactly the way 안 does.
❌ 못 공부해요.
mot gongbuhaeyo
Wrong position — 못 goes after the noun.
✅ 공부 못 해요.
gongbu mot haeyo
I can't study.
4. Using 안 when you mean "couldn't." If the truth is that you tried and failed, 안 misreports it as a deliberate choice. Reach for 못.
❌ 어제 잠을 안 잤어요.
eoje jameul an jasseoyo
Says you chose to stay up — not 'I couldn't sleep.'
✅ 어제 잠을 못 잤어요.
eoje jameul mot jasseoyo
I couldn't sleep last night.
5. Using 안 for a physical inability. 술을 안 마셔요 is a fine sentence, but if your body genuinely can't handle alcohol, it misstates the reason as preference. Say 못.
❌ 저는 술을 안 마셔요.
jeoneun sureul an masyeoyo
Says you choose not to — wrong if you physically can't.
✅ 저는 술을 못 마셔요.
jeoneun sureul mot masyeoyo
I can't drink alcohol. (no tolerance)
Key Takeaways
- 안 = won't / doesn't / isn't (choice or plain fact). 못 = can't (blocked by ability, circumstance, or permission).
- Descriptive verbs (adjectives) take only 안 — there's no "unable to be" a state.
- 하다-verbs split the negator: 공부 안 해요 / 공부 못 해요, never ×안 공부해요.
- Long forms mirror the short: -지 않다 for 안, -지 못하다 for 못 (못해요 → [모태요]).
- When in doubt, ask: unwilling (안) or unable (못)?
For each negator alone, see 안 short negation and 못 for inability; for the long form, -지 못하다; and for a deeper contrast, 못 vs 안.
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Start learning Korean→Related Topics
- Short Negation: 안TOPIK 1 — The everyday 'not' — how the adverb 안 negates verbs and adjectives, why noun+하다 action verbs split into 공부 안 해요, and how 안 (won't/don't by choice) differs from 못 (can't).
- 못: Can't / InabilityTOPIK 1 — The adverb 못 negates ability, not choice — 못 가요 'can't go', 못 먹어요 'can't eat'. It sits before the verb, splits noun+하다 verbs the way 안 does (공부 못 해요), attaches only to action verbs, and hides two tricky pronunciations: 못 해요 [모태요], 못 가요 [몯까요].
- Long Inability: -지 못하다TOPIK 2 — The formal, written counterpart of short 못 — attach -지 to any stem and let 못하다 carry tense and politeness (가지 못해요, 참석하지 못했습니다). Same 'can't' meaning, but it never splits noun+하다 verbs and fits the parallel 못 : -지 못하다 :: 안 : -지 않다.
- 못 vs 안: Can't vs Won'tTOPIK 1 — The semantic split that Korean forces you to make: 안 negates choice or plain fact ('doesn't / won't'), while 못 negates ability blocked by circumstance ('can't, though I might want to').