An anniversary is a day that commemorates an event that occurred on the same day of the year some time in the past.

Birthdays are the most common type of anniversary where the birth date of a person is commemorated.

Wedding anniversaries are also often celebrated on the same day of the year as the wedding occurred.

Most countries around the world celebrate national anniversaries. These can be the date of independence of the nation or the adoption of a new constitution or form of government.

Many anniversaries have special names; for example 25 years is a Silver Jubilee or silver wedding anniversary; 50 years is a Golden Jubilee; 60 years is a Diamond Jubilee; 70 years is a Platinum Jubilee. Generally speaking the longer the period, the more precious the material associated with it. Anniversaries of nations are usually given by the number of years elapsed in Latin. However, the word is often incorrectly used for different time lengths (eg. a "one month anniversary").

Anniversary names

• Triennial - 3 years
• Quadrennial - 4 years
• Quinquennial - 5 years
• Sexennial - 6 years
• Septennial - 7 years
• Octennial - 8 years
• Novennial - 9 years
• Decennial - 10 years
• Vigennial - 20 years
• Semicentennial - 50 years
• Demisesquicentennial - 75 years
• Centennial - 100 years
• Quasquicentennial - 125 years
• Sesquicentennial - 150 years
• Terquasquicentennial - 175 years
• Bicentennial - 200 years
• Tercentennial or tricentennial - 300 years
• Quadricentennial - 400 years
• Quincentennial - 500 years
• Sexacentennial - 600 years
• Septuacentennial - 700 years
• Octocentennial - 800 years
• Nonacentennial - 900 years
• Millennial - 1000 years
• Bimillennial - 2000 years