This is the 266th most frequent Japanese word.
周年
"Shūnen" (周年) means "anniversary" in English.
周年 is used to highlight the commemoration of the 50th year since the establishment of the company.
この会社は来年で創立50周年を迎えます。
This company will celebrate its 50th anniversary next year.
周年 describes a significant time period, in this case, a century since the founding of the university.
大学は100周年記念行事を開催しました。
The university hosted an event to commemorate its 100th anniversary.
周年 refers to the 10th anniversary of marriage, used to mark the annual recurrence of this event.