Nouns - Nominalising

것 is attached descriptive forms of verbs an adjectives to nominalise them, i.e. make them nouns.

• 하다 → 하는 (Descriptive I)
• 하는 + 것 = 하는 것 = something that you do

• 하다 → 한 (Descriptive II)
• 한 + 것 → 한 것 = something that you did

• 크다 → 큰 (Descriptive)
• 큰 + 것 = 큰 것 = something that is big / large

Nominalised Verbs (Descriptive I)

• 하는 것 = something that you do / that does
• 가는 것 = something that goes
• 오는 것 = something that comes
• 먹는 것 = something that you eat (food)
• 마시는 것 = something that you drink 
• 읽는 것 = something that you read 
• 듣는 것 = something that you listen
• 말하는 것 = something that speaks / you talk about
• 보는 것 = something that you watch
• 쓰는 것 = something that you write / use
• 만드는 것 = something that you make

Nominalised Verbs (Descriptive II)

• 한 것 = something that you did
• 간 것 = something that went
• 온 것 = something that came
• 먹은 것 = something that you ate 
• 마신 것 = something that you drank 

Nominalised Adjectives (Descriptive)

• 많은 것 =  something that is many (in quantity)
• 적은 것 = something that is small (in quantity)
• 큰 것 = something that is big / large
• 작은 것 = something that is small
• 넓은 것 = something that is spacious
• 좁은 것 = something that is cramped
• 높은 것 = something that is high
• 낮은 것 = something that is low
• 빠른 것 = something that is fast
• 느린 것 = something that is slow
• 긴 것 = something that is long
• 짧은 것 = something that is short

Note: However, in spoken Korean 것 is pronounced 거.
e.g.

• 하는 거 = something that you do
• 긴 거 = something that is long

Also, attach 야 to 거 to make it informal spoken form, or 에요 make it a polite spoken form.

• 하는 거야
• 긴 거야

• 하는 거예요
• 긴 거예요

When a plural form is used, 들 is attached to 것 instead.

• 하는 것들 = things that we do
• 긴 것들 = things that are long

Example sentences

• 이 노트북이 가장 빠른 거예요 = This laptop is the one that is the fastest.

• 이 과일주스 병들은 다 마신거예요 = These bottles of fruit juice are all what we drank from already.

• 이 음식들도 오늘 먹는 거예요? = Are these food something that we eat today as well? (=Are we going to eat these food today as well?)

• 지금 티비 보는 거예요? = Is TV something you're watching now? (= Are you watching TV now?)

• 이 물고기들은 다 어제 바다에서 잡은 것들이에요 = These fish are all what I caught at the sea yesterday.