This is the 10847th most frequent Korean word.
그리울
"그리울" means "to be missed" or "longed for."
Here, "그리울" conveys the sense of longing for something or someone absent, modifying "추억," meaning memories.
그리울 추억이 가슴 속에 담겨 있어요.
Fond memories are kept in my heart.
In this sentence, "그리울" describes the missing friend whom the speaker is looking forward to seeing.
그리울 친구와의 만남을 기다리고 있어요.
I am waiting for a reunion with a friend I miss.
"그리울" in this context refers to days the speaker feels nostalgic about and misses.