This is the 10045th most frequent Korean word.
공지문이다
"It is an announcement."
In this context, '공지문이다' emphasizes that the message is a formal notification from the school.
이것은 학교의 공지문이다.
This is a school's announcement.
Here, '공지문이다' refers to a document highlighting the official announcement.
회사가 새로운 정책을 공지문이다.
The company announced the new policy through a notice.
In this usage, '공지문이다' indicates the content explicitly labeled as a notice.