This is the 9977th most frequent Korean word.
공부했다
"Studied."
In this sentence, '공부했다' means 'studied', referring to engaging in the act of studying during the previous night.
나는 어제 밤새 공부했다.
I studied all night yesterday.
Here, '공부했다' indicates that the person had studied adequately, implying preparation for the given exam.
많이 공부했다니 시험을 잘 볼 거야.
Since you studied a lot, you will do well on the exam.
In this case, '공부했다' conveys effortful study aimed towards achieving a long-term goal or improvement.