English lumps "not" and "can't" together with a shrug — I don't eat meat, I can't eat this. Korean draws a hard grammatical line between choosing not to (안 / -지 않다) and being unable to (못 / -지 못하다), and it offers each in a short form (a little adverb before the verb) and a long form (a tail on the stem). That gives four tools. This page tables all four, then handles the three things that actually trip English speakers: adjectives can't take 못, 하다-verbs break apart under short negation, and "don't do that!" is a separate construction, not 안.
The four strategies
| Strategy | Type | Meaning | 가다 example | 먹다 example | Works on adjectives? |
|---|---|---|---|---|---|
| 안 + verb | short | plain "not / doesn't" | 안 가요 an gayo | 안 먹어요 an meogeoyo | Yes — 안 좋아요 |
| 못 + verb | short | "can't" (inability) | 못 가요 mot gayo | 못 먹어요 mot meogeoyo | No — ✗못 좋아요 |
| -지 않다 | long | plain "not" (= long 안) | 가지 않아요 gaji anayo | 먹지 않아요 meokji anayo | Yes — 좋지 않아요 |
| -지 못하다 | long | "can't" (= long 못) | 가지 못해요 gaji motaeyo | 먹지 못해요 meokji motaeyo | Rarely |
Short and long are near-synonyms: 안 가요 and 가지 않아요 both mean "doesn't go." Short 안 / 못 are lighter and dominate speech; the long -지 않다 / -지 못하다 are a touch more deliberate and are the default in writing and for longer verb phrases. The meaning split — volition (안) vs ability (못) — is the same in both. For the choice, see 안 vs 못.
저는 아침을 안 먹어요.
jeoneun achimeul an meogeoyo
I don't eat breakfast. (I choose not to.)
오늘은 시간이 없어서 못 가요.
oneureun sigani eopseoseo mot gayo
I can't make it today — I don't have time. (unable)
그 얘기는 별로 좋지 않아요.
geu yaegineun byeollo jochi anayo
That story isn't really good. (long negation of an adjective)
매워서 더는 못 먹겠어요.
maewoseo deoneun mot meokgesseoyo
It's too spicy — I can't eat any more.
Trap 1: 못 does not negate adjectives
못 means "lacks the ability to," and a quality like good or pretty isn't something you have the ability to do — so 못 can't touch a descriptive verb. To say something isn't good, use 안 or -지 않다.
날씨가 안 좋아요.
nalssiga an joayo
The weather isn't good.
이 방은 별로 깨끗하지 않아요.
i bang-eun byeollo kkaekkeutaji anayo
This room isn't very clean.
Trap 2: 하다-verbs split under short negation
A noun + 하다 verb (공부하다, 운동하다, 전화하다) is really "noun + do." Under short 안 / 못, the negator wedges between the noun and 하다 — you negate the "doing," so the adverb sits right before 해요. The long form does not split.
| Verb | Short 안 (splits) | Short 못 (splits) | Long -지 않다 (no split) |
|---|---|---|---|
| 공부하다 | 공부 안 해요 gongbu an haeyo | 공부 못 해요 gongbu mot haeyo | 공부하지 않아요 gongbuhaji anayo |
| 운동하다 | 운동 안 해요 undong an haeyo | 운동 못 해요 undong mot haeyo | 운동하지 않아요 undonghaji anayo |
저 요즘 운동 안 해요.
jeo yojeum undong an haeyo
I don't work out these days. (하다-verb splits: 운동 안 해요)
어제 몸이 아파서 공부 못 했어요.
eoje momi apaseo gongbu mot haesseoyo
I couldn't study yesterday because I felt sick.
The split hits only genuine noun + 하다 pairs. A single-word verb like 좋아하다 ("to like") does not split — you say 안 좋아해요, not ×좋아 안 해요, because 좋아 isn't a free-standing noun. See the 하다 paradigm for which 하다-words split.
Trap 3: "Don't!" is -지 마세요, not 안
Negative commands are a construction of their own — the auxiliary 말다 as -지 마 / -지 마세요 (and propositive -지 맙시다 / -지 말자). 안 negates statements, not orders; putting 안 on a command yields a statement instead.
여기서 사진 찍지 마세요.
yeogiseo sajin jjikji maseyo
Please don't take photos here.
걱정하지 마. 다 잘될 거야.
geokjeonghaji ma. da jaldoel geoya
Don't worry. It'll all work out. (반말)
Full imperative and propositive forms across every level are on the imperative & propositive table.
Suppletive negatives: 없다 and 모르다
Two very common verbs replace their negative with a whole different word rather than adding 안. "Exist / have" is 있다, and its negative is 없다 (not ×안 있다). "Know" is 알다, and its negative is 모르다 (not ×안 알다). Learn the pair, not the negator.
지갑이 어디 갔지? 여기 없어요.
jigabi eodi gatji? yeogi eopseoyo
Where'd my wallet go? It's not here. (있다 → 없다)
어? 저는 그거 몰랐어요.
eo? jeoneun geugeo mollasseoyo
Huh? I didn't know that. (알다 → 모르다)
The 없다 forms live on the 없다 paradigm.
Common Mistakes
1. Not splitting a 하다-verb under short 안. The negator goes between the noun and 하다.
❌ 저는 요즘 안 운동해요.
Wrong — a noun + 하다 verb splits under short 안: 운동 안 해요.
✅ 저는 요즘 운동 안 해요.
jeoneun yojeum undong an haeyo
I don't work out these days.
2. Negating an adjective with 못. Qualities take 안 / -지 않다, never 못.
❌ 오늘 날씨가 못 좋아요.
Wrong — 못 is for inability; an adjective takes 안: 안 좋아요.
✅ 오늘 날씨가 안 좋아요.
oneul nalssiga an joayo
The weather isn't good today.
3. Using 안 알아요 / 안 있어요 instead of the suppletive verb. These take 모르다 / 없다.
❌ 저는 그 사람 안 알아요.
Wrong — the negative of 알다 is 모르다: 몰라요.
✅ 저는 그 사람 몰라요.
jeoneun geu saram mollayo
I don't know that person.
4. Using 안 for a prohibition. "Don't go" is a command → -지 마세요; 안 가세요 just describes ("you don't go").
❌ 위험하니까 안 가세요.
Wrong — for 'don't go' use the prohibition -지 마세요, not 안: 가지 마세요.
✅ 위험하니까 가지 마세요.
wiheomhanikka gaji maseyo
It's dangerous, so please don't go.
Key Takeaways
- Four strategies: short 안 / 못 (adverb before the verb) and long -지 않다 / -지 못하다 (tail on the stem).
- The core split English merges: 안 = plain "not" / choosing not to; 못 = "can't" / unable.
- 못 doesn't negate adjectives — qualities take 안 or -지 않다 (안 좋아요, not ✗못 좋아요).
- 하다-verbs split under short negation (공부 안 해요), but not under the long form (공부하지 않아요).
- Prohibitions are -지 마세요 / -지 마, a separate construction from 안.
- Some negatives are suppletive: 있다 → 없다, 알다 → 모르다.
Now practice Korean
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Start learning Korean→Related Topics
- 하다 (to do): Complete Paradigm, All Tenses × LevelsTOPIK 1 — The exhaustive reference grid for 하다 — the single highest-leverage verb in Korean, since thousands of noun+하다 verbs (공부하다, 사랑하다, 운동하다) inherit every one of its cells. Present, past, future, progressive, imperative, propositive, connectives, attributives, and nominal forms, all driven by one contraction: 하 + 여 → 해.
- Imperative & Propositive Across All Speech LevelsTOPIK 2 — A focused look-up table for commands (imperative) and suggestions (propositive) — the two moods that vary most by speech level and trip learners most. Rows by level, columns splitting a vowel stem from a consonant stem to show 으-insertion, plus the negative-command row and the crucial 'don't aim -(으)ㅂ시다 upward' caveat.
- 없다 (to not exist / to not have): ParadigmTOPIK 1 — The full look-up paradigm of 없다, the suppletive negative of 있다 — Korean has no productive 'not-있다,' you switch to the separate word 없다 — across all four speech levels, with the verbal -는 attributive (없는, never ×없은) and the key warning that ×안 있어요 is not how you say 'there isn't.'
- 안 vs 못: Won't or Can'tTOPIK 1 — Both negate the verb, but 안 negates by choice or plain fact ('do not / is not') while 못 negates by inability ('cannot' — blocked by capacity, circumstance, or permission); the deciding line is volition versus impossibility.
- Prohibition: -지 마(세요) — 'Don't'TOPIK 1 — Korean builds 'don't' not from a negated imperative but from a dedicated construction: verb + -지 말다 ('desist from doing'). Because 말다 is a ㄹ-stem, the ㄹ drops before the endings, giving 마세요 / 마 / 마십시오 — never ✗말으세요 or ✗말세요.