Two negators, one slot
Korean uses two single-syllable negators that sit right before the verb: 안 says you don't / aren't / won't (a chosen non-action), and 못 says you can't (an inability or external block). 안 가요 = 'I don't go.' 못 가요 = 'I can't go.' For 하다-compound verbs, the negator splits the noun from 하다: 공부 안 해요, 공부 못 해요.
안 — voluntary negation
안 = simple 'not'. Place it directly before the verb or adjective: 안 가요 ('don't go'), 안 먹어요 ('don't eat'), 안 좋아요 ('not good'), 안 비싸요 ('not expensive'). It works in any tense: 안 갔어요 ('didn't go'), 안 갈 거예요 ('won't go'). There is also a longer form -지 않아요 with the same meaning (가지 않아요 = 'don't go'); both are correct, 안 is more conversational.
못 — inability / impossibility
못 = 'can't'. Same slot, right before the verb. 못 가요 = 'I can't go' (something is preventing me — busy, sick, blocked). 못 먹어요 = 'I can't eat (it)' — maybe an allergy, maybe it's too spicy. The contrast: 안 먹어요 is a choice, 못 먹어요 is an inability. Like 안, it works across tenses: 못 갔어요, 못 갈 거예요. Long form: -지 못해요 (가지 못해요 = 'can't go').
The 하다-verb split
Verbs like 공부하다, 일하다, 운동하다, 사랑하다, 전화하다 look like one word but behave like 'noun + 하다'. The negator goes between the noun and 하다, not in front: 공부 안 해요 ('don't study'), not *안 공부해요. Same for 못: 공부 못 해요 ('can't study'). Long forms keep the verb intact: 공부하지 않아요, 공부하지 못해요.
Pronunciation note: 못
못 ends in ㅅ, but in real speech it usually sounds like the front of the next word. 못 가요 is said roughly 'mot kayo' but you'll often hear 'mok-kayo' (assimilation to ㄱ). 못 해요 sounds like 'mo-tae-yo'. Spelling stays 못 — just say it naturally.
Don't double-negate
Unlike English, Korean usually picks one negator. 'I don't not go' is not how Koreans express 'I do go' — they just say 가요 or, for emphasis, 가요, 가요 ('I'm going, I'm going')! Stack a negator only when the meaning genuinely needs it: e.g. 모르지 않아요 ('it's not that I don't know') is rare and emphatic.
