ㄴ 거 쓰다

use, wear, or write ___ one

-ㄴ 거 means 'the ___ one' and 쓰다 supplies the action, which depends entirely on the object: use a product (되게 비싼 거 쓴대요), wear a hat (엄청 조그만 거 쓰겠네요), spend money (큰 거 써야될 때), or write something (미안한 거 썼어). Korean packs all of these into one verb, so the noun implied by 거 is what tells you which reading is meant.

Register: casual