There is a sea of explanations on these grammar points available on the internet. Some of them are a bit technical so I decided to use practical examples to illustrate their difference.
-기 vs -는 것
Consider this situation: I am taking a walk with my wife, and she says “hold my hand”. I reply “I don’t wanna hold hands”. Consider two options here:
- 손 잡기 싫어
- 손 잡는 것이 싫어
Option one is a response to this particular instance. You don’t want to hold her hand now. It’s not that you don’t like holding her hand in general, or you don’t like holding hands in general. Contrast with option two, which means you don’t like holding hands as a general fact about yourself. In this scenario of course option one is better.
Consider another situation: You are visiting someone for the first time and when you get there you say to them “it was easy to find your house”. You have two options:
- 집 찾기가* 쉬웠어요 (the sentence is more natural with 가 but this is beyond the scope here)
- 집 찾는 것이 쉬웠어요
Option one means finding this house was easy while option two means finding houses as a general thing/activity was easy.
Some examples for your to consider. If you leave a comment below I can explain which one means what.
- 혼자 있기 싫어요 vs 혼자 있는 것이 싫어요
- 술 먹기 싫어요 vs 술 먹는 것이 싫어요
- 공부하기 싫어요 vs 공부하는 것이 싫어요
What about -음
This is more complicated than the other two and can get quite difficult to use in practise.
I’ll begin with an illustration: you are talking to your friend about dying and that you’re scared of dying. You have the options of:
- 죽기가 무서워요
- 죽는 것이 무서워요
- 죽음이 무서워요
One and two are closer to each other because they both refer to the act of dying or in English “dying is scary”. 죽음 is different. It means “death is scary”. Death isn’t a verb that has been turned into a noun, it is a concept. It’s like turning a verb into a concept.
There are some common examples using 음:
- 자다 -> 잠. The verb sleep has been turned into sleep
- 꾸다 -> 꿈. The verb dream has been turned into dream
- 볶다 -> 볶음. The verb fry has been turned into fried food (like 볶음밥 which is fried rice)
- 예쁘다 -> 예쁨. The adjective pretty has been turned into prettiness
- 못생기다 -> 못생김.
The usage of 음 can be further generalised in formal contexts, which as learners we almost never have to deal with. If you ever need to generalise a verb or adjective into a concept/noun, you will be better off using the 는/은다는 것 pattern which you can read about here.