못: Can't / Inability | Korean Grammar

Where 안 says "not by choice," 못 says "can't." It's the adverb of inability: you drop it right in front of the verb — 못 가요 "can't go," 못 먹어요 "can't eat," 못 자요 "can't sleep" — to mark that the action is blocked, not declined. Something is stopping it: your body, your circumstances, the rules, the lack of time or skill. This is a distinction English smears together under one word "can't/won't," and Korean insists you keep them apart.

The basic rule: 못 goes in front

Placement is identical to 안. Put 못 immediately before the verb; it's a free-standing adverb, so it doesn't attach or conjugate. The verb takes its normal ending.

오늘은 못 가요.

oneureun mot gayo

I can't go today.

너무 매워서 못 먹어요.

neomu maewoseo mot meogeoyo

It's too spicy, so I can't eat it.

시끄러워서 잠을 못 자요.

sikkeureowoseo jameul mot jayo

It's so noisy I can't sleep.

The tense sits on the verb, exactly as with 안 — 못 itself never changes across present, past, or future.

아파서 학교에 못 갔어요.

apaseo hakgyoe mot gasseoyo

I was sick, so I couldn't go to school.

What 못 means: blocked, not chosen

The heart of 못 is external or physical obstruction. The subject wants (or would be willing) to do the action, but can't — because of ability, capacity, circumstance, or permission. Line these up against 안 and the contrast is sharp:

안 (choice / plain fact)	못 (blocked ability)
술을 안 마셔요 — I don't drink (I choose not to)	술을 못 마셔요 — I can't drink (my body can't handle it)
파티에 안 갔어요 — I didn't go (didn't feel like it)	파티에 못 갔어요 — I couldn't go (something stopped me)

저는 매운 걸 못 먹어요.

jeoneun maeun geol mot meogeoyo

I can't eat spicy food. (my tolerance won't allow it)

어제 잠을 못 잤어요.

eoje jameul mot jasseoyo

I couldn't sleep last night.

That second sentence doesn't mean you chose to stay awake — it means sleep wouldn't come. Choosing 안 잤어요 there would say you deliberately didn't sleep, which is a different (and slightly alarming) claim.

💡

Ask yourself: is a reason blocking the action — no time, no ability, sick, not allowed? Then 못. Is it your preference — you just don't want to? Then 안. English "I can't come to the party" is ambiguous between these; Korean forces you to pick, and picking wrong changes the whole social message.

The noun+하다 split — same as 안

Just like 안, 못 splits noun+하다 action verbs down the middle. It wedges between the noun and 하다, not out in front of the whole word.

Verb	Wrong	Right
공부하다	✗ 못 공부해요	공부 못 해요
운동하다	✗ 못 운동해요	운동 못 해요
운전하다	✗ 못 운전해요	운전 못 해요

요즘 바빠서 운동 못 해요.

yojeum bappaseo undong mot haeyo

I'm busy these days, so I can't work out.

다쳐서 한동안 운전 못 해요.

dacheoseo handongan unjeon mot haeyo

I got hurt, so I can't drive for a while.

The logic is the same as with 안: 공부하다 is really "do studying," and 못 negates the doing, so it slips in right before 하다. If the split gives you trouble, the long form -지 못하다 avoids it entirely — 공부하지 못해요.

못 attaches only to action verbs — never adjectives

This is a hard boundary. 못 negates ability to do an action, so it can only sit on action verbs. You cannot be "unable to be pretty" or "unable to be expensive" — states aren't actions you either can or can't perform. Adjectives (descriptive verbs) take 안 or -지 않다, never 못.

❌ 이 옷은 못 예뻐요.

Incorrect — 예쁘다 is an adjective; you can't be 'unable to be pretty'.

✅ 이 옷은 안 예뻐요.

i oseun an yeppeoyo

This outfit isn't pretty.

The one apparent exception is 잘하다 / 못하다 ("be good at / be bad at"), but there 못하다 is a single lexical verb meaning "to be poor at," not the adverb 못 on an adjective — a different creature entirely. For ordinary descriptions like 크다, 비싸다, 좋다, only 안 works.

Pronunciation: 못 hides two sound changes

못 ends in ㅅ, and that final consonant reshapes the boundary with the next word. The spelling stays 못, but two pronunciations are worth memorizing because they sound nothing like the letters:

못 해요 → [모태요]. The ㅅ (neutralized to [ㄷ]) fuses with the following ㅎ into an aspirated ㅌ. So 공부 못 해요 comes out [공부 모태요].
못 가요 → [몯까요]. The following ㄱ tenses to [ㄲ], and 못 ends in a hard [ㄷ] stop. Likewise 못 봐요 → [몯뽜요], 못 자요 → [몯짜요].

한국어를 아직 잘 못해요.

hangugeoreul ajik jal motaeyo

I still can't speak Korean well. (한국어를 잘 못해요, pronounced [잘 모태요])

Don't let the spelling fool your ear or your mouth: 못 해요 is [모태요], not "mot-hae-yo" pronounced letter by letter. This is the same aspiration you'll see spelled out in the single word 못하다 [모타다].

💡

The written form always stays 못 — the sound changes are automatic and never spelled out. So when you hear [모태요] or [몯까요] and go to write it, resist the urge to spell what you heard: it's 못 해요 and 못 가요 on the page, every time.

Common Mistakes

1. Using 못 with an adjective. States take 안, not 못.

❌ 오늘 날씨가 못 좋아요.

Incorrect — 좋다 is an adjective; use 안 좋아요.

✅ 오늘 날씨가 안 좋아요.

oneul nalssiga an joayo

The weather isn't good today.

2. Failing to split a noun+하다 verb. 못 wedges before 하다, just like 안.

❌ 시간이 없어서 못 공부해요.

Incorrect — split it: 공부 못 해요.

✅ 시간이 없어서 공부 못 해요.

sigani eopseoseo gongbu mot haeyo

I have no time, so I can't study.

3. Reaching for 못 when you mean choice. If nothing is blocking you and you simply won't, that's 안.

❌ 저는 그 영화를 못 봐요.

Misleading if you just don't want to watch it — that's 안 봐요.

✅ 저는 그 영화를 안 봐요.

jeoneun geu yeonghwareul an bwayo

I don't watch that movie. (by choice)

4. Pronouncing 못 해요 letter by letter. It's [모태요], with an aspirated ㅌ.

✅ 아직 요리를 잘 못해요.

ajik yorireul jal motaeyo

I still can't cook well. (잘 못해요 → [잘 모태요])

Key Takeaways

못 goes directly before the verb and means "can't" — the action is blocked by ability, circumstance, or permission, not declined.
It contrasts with 안 ("won't / don't by choice"): 술을 못 마셔요 (can't) vs 술을 안 마셔요 (choose not to).
Noun+하다 action verbs split the same way as with 안: 공부 못 해요, not ✗못 공부해요.
못 attaches only to action verbs, never to adjectives (✗못 예뻐요 → 안 예뻐요).
Watch the pronunciation: 못 해요 [모태요], 못 가요 [몯까요]. For the formal/written equivalent, use -지 못하다.

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