noun
Refers to a holiday established by law or regulation, such as national holidays or designated public holidays.
明日は公休日なので、会社は休みです。
Tomorrow is a legal holiday, so the office is closed.
休日 is a broader term for any day off, including weekends and personal leave, whereas 公休日 is limited to official public holidays.
Compound of 公 (public, official) + 休 (rest) + 日 (day). The term directly describes a day of rest designated by public authority.