This is the 1480th most frequent Korean word.
프로야구
"프로야구" means "professional baseball."
Here, '프로야구' is used as a noun to signify the sport 'professional baseball'.
그는 프로야구 경기를 아주 좋아합니다.
He really enjoys watching professional baseball games.
In this sentence, '프로야구' operates as a modifier to define 'players' as belonging to 'professional baseball'.
프로야구 선수들은 엄격한 훈련을 받습니다.
Professional baseball players undergo rigorous training.
Here, '프로야구' is the subject of the sentence, referring to the organized league of professional baseball in Korea.