This is the 494th most frequent Korean word.
마음을
"마음을" means "heart" or "mind" in the objective case.
In this sentence, "마음을" represents the emotional inner feeling of the person, symbolizing openness.
그는 마음을 열었다.
He opened his heart.
Here, "마음을" indicates one’s decision or attitude, representing a shift in perspective.
나는 그의 이야기를 듣고 마음을 바꿨다.
After hearing his story, I changed my heart/mind.
In this context, "마음을" conveys the emotional pain or sorrow the person is experiencing.