This is the 605th most frequent Korean word.
축구
Soccer.
Here, '축구' functions as a descriptor to the noun '연습' (practice), forming the compound noun '축구 연습' (soccer practice), describing the activity practiced.
어제는 축구 연습을 하느라 많이 뛰었어요.
Yesterday, I ran a lot because of soccer practice.
Here, '축구' is used as a direct object in the sentence, representing the activity of playing soccer.
나는 매주 친구들과 함께 축구를 합니다.
I play soccer with my friends every week.
In this sentence, '축구' describes the type of game being watched, acting as part of the compound noun '축구 경기' (soccer game).