Korean turns verbs and adjectives into nouns with two little suffixes: -기 and -(으)ㅁ. You have already met their products without noticing — 읽기 "reading," 쓰기 "writing," 죽음 "death," 웃음 "a laugh," 삶 "life." This page is a pointer, not the full treatment: it exists so that when a frozen nominalization shows up in the valency and voice pages (믿음 "belief," 웃음 "laughter," 죽음 "death"), you recognize where it came from. The deep questions — when each suffix is required, how to nominalize a whole clause, and the three-way fight between -기, -(으)ㅁ, and 것 — are answered in the Syntax group, at -기 vs -(으)ㅁ vs 것. Here you just need the map.
-기: the activity noun
-기 makes an activity or gerund noun — the doing of something, treated as an ongoing or general act. It attaches to any verb or adjective stem with no allomorphy at all: stem + 기.
The four language skills are the classic set: 읽다 → 읽기 "reading," 쓰다 → 쓰기 "writing," 듣다 → 듣기 "listening," 말하다 → 말하기 "speaking."
저는 듣기보다 말하기가 더 어려워요.
jeoneun deutgiboda malhagiga deo eoryeowoyo
For me, speaking is harder than listening.
시험에 듣기 문제가 많아요.
siheome deutgi munjega manayo
There are a lot of listening questions on the test.
읽기가 생각보다 어려워요.
ilgiga saenggakboda eoryeowoyo
Reading is harder than I expected.
Because -기 names an activity, it also heads a cluster of high-frequency grammar patterns — 기 때문에 "because," 기 위해(서) "in order to," 기 전에 "before," 기 시작하다 "start to." In these you are nominalizing a verb precisely so a postposition or another verb can attach to it.
비가 오기 때문에 경기가 취소됐어요.
biga ogi ttaemune gyeonggiga chwisodwaesseoyo
The game was cancelled because it's raining.
건강을 지키기 위해 매일 운동해요.
geongang-eul jikigi wihae maeil undonghaeyo
I exercise every day to stay healthy.
-(으)ㅁ: the fact/result noun
-(으)ㅁ makes a more abstract, resultative noun — the fact, result, or state rather than the activity: 죽다 → 죽음 "death," 웃다 → 웃음 "laughter, a smile," 믿다 → 믿음 "belief, faith," 꾸다 → 꿈 "a dream," 아프다 → 아픔 "pain," 기쁘다 → 기쁨 "joy," 슬프다 → 슬픔 "sorrow."
그의 죽음이 온 나라를 슬프게 했어요.
geuui jugeumi on narareul seulpeuge haesseoyo
His death saddened the whole country. (literary/news register)
아기의 웃음이 참 예뻐요.
agiui useumi cham yeppeoyo
The baby's laugh is really lovely.
웃음이 나왔어요.
useumi nawasseoyo
A laugh burst out of me. (I couldn't help laughing)
사람에 대한 믿음을 잃지 마세요.
sarame daehan mideumeul ilchi maseyo
Don't lose your faith in people.
The batchim rule for -(으)ㅁ
Whether you write -ㅁ or -음 depends on the stem's ending:
| Stem ends in… | Suffix | Examples |
|---|---|---|
| a vowel | -ㅁ | 꾸다 → 꿈, 자다 → 잠, 추다 → 춤, 아프다 → 아픔, 기쁘다 → 기쁨 |
| a consonant | -음 | 죽다 → 죽음, 웃다 → 웃음, 믿다 → 믿음 |
| ㄹ | usually -ㅁ (cluster) | 살다 → 삶, 알다 → 앎, 만들다 → 만듦 |
좋은 삶을 살고 싶어요.
joeun salmeul salgo sipeoyo
I want to live a good life. (살다 → 삶)
어젯밤에 이상한 꿈을 꿨어요.
eojetbame isanghan kkumeul kkwosseoyo
I had a strange dream last night. (꾸다 → 꿈)
The rough division of labour — and why it's only rough
The intuition that carries you a long way: -기 = the activity, -(으)ㅁ = the fact or result. English does something similar with its own two families of suffixes — -ing for the activity (read → reading, swim → swimming) and -tion / -ment / -th for the result or abstract fact (die → death, believe → belief, move → movement). 읽기 is "reading (the activity)"; 죽음 is "death (the fact/event)."
But treat this as a signpost, not a law. Both suffixes are only semi-productive: many verbs simply do not have a lexicalized -음 noun, and where they don't, Korean reaches for the bound noun 것 (먹는 것 "the eating / what one eats") to nominalize instead. You cannot freely coin 먹음 the way English coins "the eating." Which nominalizer a given clause requires — and when only 것 will do — is genuinely intricate, and it is the whole subject of the Syntax nominalization pages: -기, -(으)ㅁ, and -는 것.
Frozen nominalizations in the verb system
The reason this pointer sits in the Verbs group: several nouns that recur across the valency, aspect, and modality pages are frozen -(으)ㅁ or -기 forms. Recognizing them keeps you from parsing them as verbs by mistake.
그 사람의 앎이 깊어요.
geu saramui almi gipeoyo
That person's knowledge runs deep. (알다 → 앎, an -(으)ㅁ noun)
글쓰기가 취미예요.
geulsseugiga chwimiyeyo
Writing is my hobby. (쓰다 → 쓰기 in the compound 글쓰기)
Common Mistakes
1. Using -기 for a lexicalized -(으)ㅁ noun. "Death" is 죽음, never 죽기.
❌ 그의 죽기가 슬펐어요.
Wrong — the noun 'death' is 죽음: 그의 죽음이 슬펐어요.
✅ 그의 죽음이 슬펐어요.
geuui jugeumi seulpeosseoyo
His death was sad.
2. Coining a -음 noun that doesn't exist. Where there's no lexical -음 form, use -는 것.
❌ 매일 뛰음이 건강에 좋아요.
Wrong — there's no noun *뛰음; use 것: 매일 뛰는 것이 건강에 좋아요.
✅ 매일 뛰는 것이 건강에 좋아요.
maeil ttwineun geosi geongang-e joayo
Running every day is good for your health.
3. Wrong suffix on a ㄹ-stem. 살다 takes -ㅁ (삶), not -음.
❌ 살음이 힘들어요.
Wrong — the noun 'life' is 삶: 삶이 힘들어요.
✅ 삶이 힘들어요.
salmi himdeureoyo
Life is hard.
4. Confusing the frozen noun with the gerund. 잠 (the noun "sleep") is not the same as 자기 (the activity of sleeping).
✅ 잠이 보약이에요.
jami boyagieyo
Sleep is the best medicine. (the noun 잠, not 자기)
Key Takeaways
- -기 = activity/gerund noun (읽기, 쓰기, 말하기); no allomorphy; heads frames like 기 때문에, 기 위해.
- -(으)ㅁ = fact/result/abstract noun (죽음, 웃음, 믿음, 꿈, 삶). Vowel stem → -ㅁ; consonant stem → -음; ㄹ-stems are irregular.
- The rough split mirrors English -ing (activity) vs -tion/-th (result), but both Korean suffixes are only semi-productive.
- For any nominalization you can't make with a lexical -기/-음 noun, use -는 것 — see the Syntax pages here for the full system.
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Start learning Korean→Related Topics
- Choosing -기 vs -(으)ㅁ vs -는 것TOPIK 3 — A decision guide for Korean's three nominalizers: -기 for unrealized activities and set frames, -(으)ㅁ for fixed written facts, and -는 것 for everything spoken and concrete — sorted by aspect and register.
- The -기 Nominalizer (먹기 싫다, -기 쉽다)TOPIK 2 — -기 turns a verb, adjective, or whole clause into a noun naming the activity — the one Korean reaches for with predicates of emotion, evaluation, and ease/difficulty, and the fixed nominalizer locked inside patterns like -기 전에, -기 때문에, and -기로 하다.
- The -(으)ㅁ Nominalizer (written: 있음/없음)TOPIK 3 — -(으)ㅁ nominalizes a verb or adjective into a noun denoting a fact, state, or finished result — the formal, written counterpart of -기 and -는 것 that powers notice-board style (재고 없음), lexicalized nouns (믿음, 죽음, 도움), and formal fact-complements (사실이 아님을 알았다).
- The -는 것 Nominalizer (the general-purpose one)TOPIK 2 — -는 것 is the everyday, all-purpose clause nominalizer — attach an attributive ending plus 것 to turn a whole clause into a noun phrase (운동하는 것이 중요해요), conjugating for tense on the attributive and contracting to 거/게/걸/건 in speech.