Anniversary (noun)

1. A date on which an event took place in a previous year, typically one that is remembered and celebrated or marked by a ceremony.
2. The completion of a year's period of time.

Origin:

From the latin word "annus" meaning "year" and "versus" meaning "to turn".

Examples:

1. Today is our wedding anniversary.
2. The company is celebrating its 50th anniversary.
3. The anniversary of his death was coming up.
4. They were planning a surprise party for their anniversary.
5. The anniversary of the 9/11 attacks is a somber reminder of the tragedy.