-기 is a nominalization ending that turns verbs and adjectives into nouns. It's similar to English "-ing" (gerund) or "to" (infinitive), allowing you to talk about actions and states as things themselves.
Formation Rules
All Stems: -기
Add -기 directly to any verb or adjective stem:
- 가다 → 가기 (going / to go)
- 먹다 → 먹기 (eating / to eat)
- 하다 → 하기 (doing / to do)
- 읽다 → 읽기 (reading / to read)
- 쓰다 → 쓰기 (writing / to write)
- 좋다 → 좋기 (being good)
- 어렵다 → 어렵기 (being difficult)
- 쉽다 → 쉽기 (being easy)
Note: Extremely regular - no exceptions
Core Function: Making Nouns
Actions as Nouns
Treating actions as things:
- 수영하기 (swimming)
- 공부하기 (studying)
- 운동하기 (exercising)
- 요리하기 (cooking)
Now these can be subjects, objects, or topics
States as Nouns
Treating adjective states as nouns:
- 좋기 (being good / goodness)
- 어렵기 (being difficult / difficulty)
- 행복하기 (being happy / happiness)
- 힘들기 (being hard / hardship)
As Sentence Subject
-기가 + Adjective
The action/state is [adjective]:
- 한국어 배우기가 어려워요 (Learning Korean is difficult)
- 매일 운동하기가 힘들어요 (Exercising every day is hard)
- 아침 일찍 일어나기가 쉽지 않아요 (Waking up early isn't easy)
- 친구 사귀기가 중요해요 (Making friends is important)
Pattern: [Verb-기]가 + Adjective
-기는 (Topic)
As for doing X:
- 공부하기는 좋아해요 (As for studying, I like it)
- 수영하기는 재미있어요 (As for swimming, it's fun)
- 요리하기는 어려워요 (As for cooking, it's difficult)
As Object
Verb + -기를 좋아하다/싫어하다
Likes and dislikes:
- 음악 듣기를 좋아해요 (I like listening to music)
- 운동하기를 싫어해요 (I dislike exercising)
- 책 읽기를 즐거워해요 (I enjoy reading books)
Verb + -기를 원하다/바라다
Wants and desires:
- 성공하기를 원해요 (I want to succeed)
- 건강하기를 바래요 (I hope to be healthy)
- 만나기를 원해요 (I want to meet)
Decision Verbs
Deciding to do something:
- 가기로 했어요 (I decided to go)
- 먹기로 정했어요 (I decided to eat)
- 시작하기로 결심했어요 (I resolved to start)
Common Patterns
-기 전에 (Before doing)
Temporal sequence:
- 자기 전에 책을 읽어요 (I read a book before sleeping)
- 먹기 전에 손을 씻어요 (I wash hands before eating)
- 시작하기 전에 준비해요 (I prepare before starting)
-기 때문에 (Because of doing)
Reason or cause:
- 바쁘기 때문에 못 가요 (I can't go because I'm busy)
- 피곤하기 때문에 일찍 자요 (I sleep early because I'm tired)
- 비가 오기 때문에 집에 있어요 (I stay home because it's raining)
-기가 쉽다/어렵다 (Easy/difficult to do)
Evaluating difficulty:
- 이해하기가 쉬워요 (It's easy to understand)
- 발음하기가 어려워요 (It's difficult to pronounce)
- 외우기가 힘들어요 (It's hard to memorize)
-기만 하다 (Only do / Just do)
Exclusive action:
- 자기만 해요 (I only sleep / I just sleep)
- 놀기만 해요 (I only play)
- 공부하기만 해요 (I only study)
-기에 좋다 (Good for doing)
Suitable for an action:
- 걷기에 좋은 날씨예요 (It's good weather for walking)
- 공부하기에 좋은 곳이에요 (It's a good place for studying)
- 살기에 좋은 도시예요 (It's a good city to live in)
-기 시작하다 (Start doing)
Beginning an action:
- 비가 오기 시작했어요 (It started raining)
- 공부하기 시작했어요 (I started studying)
- 일하기 시작했어요 (I started working)
-기를 바라다/원하다 (Hope/want to do)
Expressing wishes:
- 성공하기를 바래요 (I hope to succeed)
- 만나기를 원해요 (I want to meet)
- 합격하기를 바라요 (I hope to pass)
Abstract Actions
General Activities
Talking about activities in general:
- 읽기, 쓰기, 듣기, 말하기 (reading, writing, listening, speaking)
- 달리기 (running)
- 수영하기 (swimming)
- 노래하기 (singing)
Skills and Abilities
Naming skills:
- 한국어 말하기 능력 (Korean speaking ability)
- 문제 해결하기 (problem solving)
- 컴퓨터 사용하기 (computer use)
With Different Verbs
Action Verbs
Physical or concrete actions:
- 걷기 (walking)
- 먹기 (eating)
- 자기 (sleeping)
- 일하기 (working)
Mental Verbs
Thinking and feeling:
- 생각하기 (thinking)
- 이해하기 (understanding)
- 기억하기 (remembering)
- 느끼기 (feeling)
Change of State
Verbs of becoming:
- 되기 (becoming)
- 시작하기 (starting)
- 끝나기 (ending)
- 변하기 (changing)
Example Sentences
As Subject
- 한국어 공부하기가 재미있어요 (Studying Korean is fun)
- 매일 운동하기가 중요해요 (Exercising every day is important)
- 일찍 일어나기가 힘들어요 (Waking up early is hard)
- 친구 만나기가 즐거워요 (Meeting friends is enjoyable)
As Object
- 저는 음악 듣기를 좋아해요 (I like listening to music)
- 수영하기를 배우고 싶어요 (I want to learn swimming)
- 매일 책 읽기를 시작했어요 (I started reading books every day)
With -기 전에
- 자기 전에 이를 닦아요 (I brush my teeth before sleeping)
- 출발하기 전에 확인하세요 (Check before departing)
- 먹기 전에 기도해요 (I pray before eating)
With -기 때문에
- 아프기 때문에 쉬어요 (I rest because I'm sick)
- 바쁘기 때문에 못 만나요 (I can't meet because I'm busy)
- 좋아하기 때문에 매일 해요 (I do it every day because I like it)
Evaluating Actions
- 발음하기가 어려워요 (Pronouncing is difficult)
- 이해하기가 쉬워요 (Understanding is easy)
- 외우기가 힘들어요 (Memorizing is hard)
Example Dialogues
Dialogue 1: Hobbies
A: 취미가 뭐예요?
(What's your hobby?)
B: 책 읽기를 좋아해요.
(I like reading books.)
A: 무슨 책 읽기를 좋아해요?
(What kind of books do you like reading?)
B: 소설 읽기를 제일 좋아해요.
(I like reading novels the most.)
Dialogue 2: Difficulty
A: 한국어 배우기가 어때요?
(How is learning Korean?)
B: 문법 이해하기가 어려워요.
(Understanding grammar is difficult.)
A: 맞아요. 저도 발음하기가 힘들어요.
(Right. For me too, pronouncing is hard.)
Dialogue 3: Plans
A: 주말에 뭐 할 거예요?
(What will you do on the weekend?)
B: 친구들과 등산하기로 했어요.
(I decided to go hiking with friends.)
A: 등산하기가 좋아요?
(Do you like hiking?)
B: 네, 운동하기에 좋아요.
(Yes, it's good for exercising.)
Dialogue 4: Daily Routine
A: 매일 운동해요?
(Do you exercise every day?)
B: 네, 아침에 조깅하기를 시작했어요.
(Yes, I started jogging in the morning.)
A: 매일 하기가 힘들지 않아요?
(Isn't doing it every day hard?)
B: 처음에는 힘들었지만 지금은 괜찮아요.
(At first it was hard, but now it's okay.)
Special Uses
Fixed Expressions
Common set phrases:
- 만나서 반갑습니다 (lit. meeting [you] is pleasant - from 만나기가 반갑다)
- 앞으로 잘 부탁드립니다 (lit. asking well toward future - 부탁하기를)
Titles and Labels
Activity names:
- 읽기 연습 (reading practice)
- 듣기 시험 (listening test)
- 말하기 대회 (speaking contest)
- 쓰기 숙제 (writing homework)
With Particles
-기가 (Subject marker)
Making it the subject:
- 공부하기가 좋아요 (Studying is good)
-기를 (Object marker)
Making it the object:
- 공부하기를 좋아해요 (I like studying)
-기는 (Topic marker)
Making it the topic:
- 공부하기는 좋아하는데... (As for studying, I like it, but...)
-기도 (Also marker)
Including the action:
- 공부하기도 해요 (I also study)
Common Mistakes
❌ Incorrect: 읽은 것을 좋아해요
Using -(으)ㄴ 것 for general liking
✅ Correct: 읽기를 좋아해요
Use -기 for general actions and habits
❌ Incorrect: 가기를 쉬워요
Wrong adjective form
✅ Correct: 가기가 쉬워요
Use -기가 before adjectives
❌ Incorrect: 먹기 전 (missing 에)
Omitting particle
✅ Correct: 먹기 전에
Always use -기 전에 together
Comparison with -(으)ㄴ/는 것
-기: More formal, general, abstract
- 수영하기를 좋아해요 (I like swimming - in general)
-(으)ㄴ/는 것: More specific, concrete instances
- 수영하는 것을 봤어요 (I saw [someone] swimming - specific instance)
Summary Table
| Pattern | Usage | Example |
|---|---|---|
| -기가 Adj | Action is [adjective] | 배우기가 어려워요 |
| -기를 V | Do the action | 읽기를 좋아해요 |
| -기 전에 | Before doing | 자기 전에 |
| -기 때문에 | Because of doing | 바쁘기 때문에 |
| -기로 하다 | Decide to do | 가기로 했어요 |
| -기 시작하다 | Start doing | 오기 시작했어요 |
Key Takeaways
- ✅ Extremely regular: Just add -기 to any stem
- ✅ Makes nouns: Turns verbs/adjectives into noun forms
- ✅ Abstract and general: Used for general actions and states
- ✅ Common patterns: -기 전에, -기 때문에, -기가 어렵다
- ✅ Subject and object: Can function as subject (-기가) or object (-기를)
- ✅ Essential for expressing: Likes/dislikes, difficulty, habits
- ✅ Different from 것: -기 is more formal and general
- ✅ No exceptions: Works identically with all verbs and adjectives
-기 is one of the most fundamental and useful grammar patterns in Korean. It allows you to talk about actions and states as nouns, making it essential for expressing preferences, evaluating difficulty, and describing habits. Master this form to naturally discuss what you like to do, what's easy or hard, and your daily activities!