This is the 6357th most frequent Korean word.
아파트의
"Of an apartment" or "apartment's".
Here, "아파트의" is used to denote possession, indicating that the window belongs to the apartment.
아파트의 창문이 깨졌어요.
The apartment's window is broken.
In this sentence, "아파트의" specifies a characteristic, identifying the entrance as being associated with the apartment.
아파트의 입구는 오른쪽에 있어요.
The apartment's entrance is on the right.
Here, "아파트의" is employed to inquire about a specific property of the apartment, namely its size.