Origin: Latin suffix -ary
Anniversary has 2 different meanings across 1 category:
the date on which an event occurred in some previous year (or the celebration of it)
"We are hosting a quiet dinner to mark our wedding anniversary next week."
A day that is an exact number of years (to the day) since a given significant event occurred. Often preceded by an ordinal number indicating the number of years.
"The couple celebrated their twentieth anniversary last week, marking exactly twenty years since they got married on June fifth."
In plain English: An anniversary is the yearly date when something special happened, like a birthday or a wedding.
"We celebrated our tenth wedding anniversary with a dinner at her favorite restaurant."
Usage: An anniversary marks the specific date each year that corresponds to the original occurrence of a significant event, such as a wedding or founding. It is often expressed using an ordinal number followed by "year," like the first or tenth anniversary.
The word comes from the Medieval Latin anniversarius, which literally means "turning year." It entered English via Middle French and originally referred to a yearly turning or cycle.