Korean -기 Nominalization: Making Verbs into Sentence Subjects
Learn how to turn Korean verbs into nouns with -기 so they can act as the subject of a sentence, as in 수영하기는 좋은 운동이에요 ('Swimming is good exercise').
By TheaFirst conversations · Yapr Learn
In English, we can say 'Swimming is good exercise' by adding -ing to a verb and putting it at the front of the sentence. Korean does something similar, but it uses the ending -기 instead of -ing. Adding -기 to a verb stem turns that verb into a noun-like form that can be the subject of a sentence. This lesson focuses only on that subject position: verb stem + -기 + 는/은 or 이/가. You will learn to say things like 수영하기는 좋은 운동이에요 and 읽기는 재미있어요. We are not looking at -기 after verbs like 좋아하다 yet; here the -기 form sits at the beginning and is what the sentence is about.
By the end, you can…
- turn a Korean action verb into a noun with -기.
- use a -기 noun as the subject of a sentence with 는/은 or 이/가.
- talk about activities like swimming, reading, and studying as sentence topics.
Listen once. Try it slowly. Then say it without looking.
Checking available voices…
수영하기는 좋은 운동이에요.
Swimming is good exercise.
su-yeong-ha-gi-neun jo-eun un-dong-i-e-yo
The -기 form 수영하기 is the subject. 는 marks it as the topic, and the rest of the sentence comments on it.
읽기는 재미있어요.
Reading is fun.
il-gi-neun jae-mi-i-sseo-yo
읽기 comes from 읽다 (to read). Use this when you want to say an activity is enjoyable in general.
한국어 배우기는 어려워요.
Learning Korean is difficult.
han-guk-eo bae-u-gi-neun eo-ryeo-wo-yo
배우기 is the subject. This pattern is useful for talking about how easy or hard an activity is.
일찍 일어나기는 힘들어요.
Getting up early is hard.
il-jjik i-reo-na-gi-neun him-deu-reo-yo
The whole phrase 일찍 일어나기 acts as one subject. The adverb 일찍 stays inside the -기 phrase.
매일 운동하기가 중요해요.
Exercising every day is important.
mae-il un-dong-ha-gi-ga jung-yo-hae-yo
Here -기 is marked with 가 because it is new information. Compare with the topic marker 는 in the first phrase.
Pronunciation guides are approximate. Slow playback keeps the original pitch.
Make it make sense
Useful pattern
The basic pattern is: verb stem + -기 + subject marker + comment. Take the dictionary form, remove 다, and add 기. 하다 becomes 하기, 읽다 becomes 읽기, 배우다 becomes 배우기. Then add 는/은 if the -기 noun is the topic, or 이/가 if it is the grammatical subject. Examples: 수영하기는 좋은 운동이에요 (Swimming is good exercise), 읽기는 재미있어요 (Reading is fun), 매일 운동하기가 중요해요 (Exercising every day is important). The -기 noun can be long, but it still counts as one subject.
When to use it
Use -기 as a subject when you are making a general statement about an activity, not about a specific person doing it right now. It is common with adjectives like 좋다 (good), 재미있다 (fun), 어렵다 (difficult), 쉽다 (easy), 중요하다 (important), and 힘들다 (hard). For example, 한국어 배우기는 어려워요 (Learning Korean is difficult) sounds like a general observation. If you want to say 'I am learning Korean now,' you would use a different pattern, not this subject -기 form. Also note that 는 often sounds more natural than 가 when you are introducing the activity as a topic.
Listen to each line, then take one part and reply out loud.
취미가 뭐예요?
What is your hobby?chwi-mi-ga mwo-ye-yo?수영하기는 좋은 운동이에요. 그래서 주말마다 수영해요.
Swimming is good exercise. So I swim every weekend.su-yeong-ha-gi-neun jo-eun un-dong-i-e-yo. geu-rae-seo ju-mal-ma-da su-yeong-hae-yo.저는 읽기는 재미있어요. 그런데 한국어 배우기는 어려워요.
For me, reading is fun. However, learning Korean is difficult.jeo-neun il-gi-neun jae-mi-i-sseo-yo. geu-reon-de han-guk-eo bae-u-gi-neun eo-ryeo-wo-yo.맞아요. 매일 운동하기가 중요해요.
That's right. Exercising every day is important.ma-ja-yo. mae-il un-dong-ha-gi-ga jung-yo-hae-yo.A little context goes a long way
In everyday Korean, -기 as a subject often sounds a little more formal or written than simply saying the activity with a regular verb. In conversation, people may prefer phrases like 수영하는 것은 좋은 운동이에요, using -는 것 instead of -기. Both are correct. -기 is common in signs, definitions, and general statements, while -는 것 can feel more conversational. Choosing 는 or 가 also changes nuance: 는 often sets a topic or contrast, while 가 highlights new information.
One thing to watch for
수영하기는 좋은 운동이에요 is fine, but learners often write 수영하기 좋은 운동이에요, dropping the subject marker.
Try this instead: When the -기 form is the subject or topic, you need a marker such as 는/은 or 이/가. Say 수영하기는 좋은 운동이에요 or 수영하기가 좋은 운동이에요. Without the marker, the sentence is incomplete or sounds like a different structure.
Your turn
Try answering out loud before checking a possible answer.
1Turn 배우다 into a -기 subject and complete: 한국어 ___ 어려워요.
Show a sample answer
한국어 배우기는 어려워요.
배우다 loses 다 and takes 기, then 는 marks it as the topic. 배우기가 is also possible if you want to highlight it as new information.
2Which marker would you use if you want to present the activity as new information rather than a topic?
Show a sample answer
이/가, for example 매일 운동하기가 중요해요.
이/가 highlights the subject as new information. 는 is also correct in many contexts, but it usually adds a topic or contrast meaning.
3Translate: 'Getting up early is hard.'
Show a sample answer
일찍 일어나기는 힘들어요.
일어나다 becomes 일어나기, and the adverb 일찍 stays before it. 일찍 일어나기가 힘들어요 is also acceptable depending on focus.
To make an activity the subject of a Korean sentence, add -기 to the verb stem and mark it with 는/은 or 이/가: 수영하기는 좋은 운동이에요. Keep the -기 phrase together as one subject, and choose 는 for topics or contrasts and 가 for new information.
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