~것 같다 (~geot gat-da) – seems like/I guess
You would usually use ~것 같다 when you are expressing your thoughts, especially when you are unsure of the facts.
When you are quite certain about what you are claiming/expressing, you would use 은/ㄴ 것 같다.
Example: 그 남자가 한국어를 잘해서 한국 사람인 것 같아
That man speaks Korean well, seems like he’s a Korean.
On the other hand, you would use 을/ㄹ 것 같다 when you know that your guess is weak, and sometimes, you can even end off with a question mark to express your uncertainty.
Example: 아마 그 여자가 나를 좋을 것 같아..?
Maybe that girl likes me..?
The person is very uncertain if the girl likes him or not, so he used 을 것 같다 to express his very weak guess.
