In short

Korean spacing (띄어쓰기, ttuieosseugi) carries meaning, and one rule does most of the work: particles and endings attach with no space, but bound nouns and counters take a space. On top of that, a small set of spelling (맞춤법, matchumbeop) pairs - 되/돼, 안/않, -이에요/-예요 - trip up even native writers, so learn them as fixed choices.

The rule

Korean is written with spaces between words, but “word” is not obvious when everything stacks onto a stem. Use these tests.

Step 1 - Particles and endings attach; never space them

A 조사 (josa, particle) glues to its noun even when several stack, and a verb ending glues to its stem:

Noun + 조사(들) (attached). 학교에서만은 (hakgyoeseomaneun) - at school, at least (as opposed to elsewhere); here 에서 + 만 + 은 all ride on 학교 with no spaces. 먹었어요 (meogeosseoyo) - ate; 먹 + 었 + 어요 is one written word.

Step 2 - Bound nouns (의존명사) take a space

A 의존명사 (uijonmyeongsa, dependent noun) cannot stand alone, but it is still a noun, so it is written separately from the modifier in front. The giveaway: a modifier ending -(으)ㄹ / -는 / -(으)ㄴ sits before it.

Verb-(으)ㄹ + 수 + 있다. 할 수 있어요 (hal su isseoyo) - can do. Others: 먹는 것 (meongneun geot) - the thing one eats; 간 적이 있다 (gan jeogi itda) - have been / have done; 온 지 (on ji) - since coming. An ordinary noun after a modifier is spaced the same way: 갈 때 (gal ttae) - when going.

Step 3 - A number and its counter are spaced

한글 맞춤법 제43항: a noun naming a unit is written separately from its number: 열 개 (yeol gae) - ten (items); 세 시 (se si) - three o’clock; 한 번 (han beon) - one time; 몇 개 (myeot gae) - how many. (제43항 다만: after a digit, or in an ordinal, the unit may be joined - 2개, 제1과, 삼학년. The month names are not counted units at all but single dictionary words, so they are always joined: 삼월 (samwol), 유월 (yuwol, never *육월), never *삼 월.) Contrast 한 번 (one time, counted) with the single word 한번 (hanbeon) - sometime / give it a try.

Step 4 - Auxiliary verbs (보조용언) are usually spaced

한글 맞춤법 제47항: spacing the auxiliary is the rule (원칙), and joining it is allowed (허용) after a -아/어 form: 도와 주다 = 도와주다 (dowa juda, dowajuda) - to help; 읽어 보다 = 읽어보다 (ilgeo boda, ilgeoboda) - to give it a read. That permission does not reach -고 있다, so 하고 있어요 (hago isseoyo) - is doing - is always spaced.

Step 5 - Negation spacing changes the meaning

The adverbs 안 and 못 are separate words, so 안 하다 (an hada) - does not do and 못 하다 (mot hada) - cannot do it (this time) are spaced. But 안되다 (andoeda) - to go wrong / turn out badly and 못하다 (motada) - to be bad at are single lexical words. Keep 안 되다 (an doeda) - does not become apart from 안되다.

Step 6 - Determiners are spaced, but 이것/그것/저것 are one word

The demonstrative determiners 이/그/저 modify a following noun and are spaced: 이 사람 (i saram) - this person, 그 책 (geu chaek) - that book. Fused pronouns are single words: 이것 (igeot) - this thing, 저것 (jeogeot) - that (over there).

Step 7 - Same syllable: particle (attached) vs bound noun (spaced)

대로 / 뿐 / 만큼 attach as particles after a noun, but are spaced as bound nouns after a verb modifier. And 및 (mit) - and and 등 (deung) - etc. are always spaced: 책 및 공책 (chaek mit gongchaek), 사과, 배 등 (sagwa, bae deung).

Forms & patterns

Attach or space - the master table:

Same word, two jobs - particle vs bound noun:

The high-frequency spelling traps (맞춤법):

Examples

Common mistakes

• 할수있어요 (halsuisseoyo) -> 할 수 있어요 (hal su isseoyo) - 수 is a bound noun, so this takes two spaces; it never fuses into one word.
• 안 되요 (an doeyo) -> 안 돼요 (an dwaeyo) - the ending -요 needs the 어 of 되어, so 되어요 contracts to 돼요, never 되요.
• 공부를 않 해요 (gongbureul anh haeyo) -> 공부를 안 해요 (gongbureul an haeyo) - 안 is the free adverb not (spaced); 않 only appears bound inside -지 않다.
• 커피이에요 (keopiieyo) -> 커피예요 (keopiyeyo) - after a vowel-final noun 이에요 contracts to 예요; the full 이에요 is only for 받침-final nouns (책이에요).
• 열개 주세요 (yeolgae juseyo) -> 열 개 주세요 (yeol gae juseyo) - a counter is a bound noun, spaced from its number: 열 개, 세 시, 한 번.

Tips

• Test 되/돼 by swapping in 하/해. Wherever the sound of 해 fits, write 돼; wherever 하 fits, write 되. 안 돼요 (해요 fits) but 되고 싶어요 (하고 fits). This one substitution settles the most common Korean typo.
• “Can I say it alone?” If a chunk can never stand by itself yet a modifier ending -(으)ㄹ/-는/-(으)ㄴ sits in front of it - 수, 것, 적, 지, 번 - it is a bound noun, so give it a space. An ordinary noun there, like 때, is spaced too.
• 안 vs 않: 안 is a whole word you could pause after (안… 가요); 않 can never open a word-slot, it only ever hides inside -지 않다. When unsure, rebuild the sentence with -지 않다 and see if 않 belongs.
• TOPIK II 쓰기 grades this. The 언어 사용 (language use) band of the writing rubric scores 맞춤법, and 띄어쓰기 is judged as part of it, so a missing space in 할 수 있어요 or a stray 되요 costs real points - proofread specifically for them.