This is the 3146th most frequent Korean word.
개학
"개학" means "the start of a school term."
Here, '개학일' specifies a particular day when the '개학', i.e., beginning of the school term, occurs.
새 학기의 개학일에 모두가 학교에 갔다.
Everyone went to school on the new semester's beginning day.
In this sentence, '개학' is used to refer to the general event or time frame when schools are starting a new term, requiring preparations.
개학 준비로 바쁜 시기다.
It's a busy period due to preparations for school opening.
Here, '개학' directly implies the action or moment of the school starting, emphasizing changes and activities tied to the commencement of the term.