What term describes the United States’ 250th anniversary, the event branded America250?

The term that describes the United States’ 250th anniversary, branded America250, is semiquincentennial.

The word combines elements meaning “half” and “five” with “centennial,” producing a term for half of five hundred years, or 250 years. It is the formal name used for the national commemoration of the anniversary of American independence.

Several alternative terms have appeared in historical and popular usage, including sestercentennial, bisesquicentennial, and quarter millennium. However, United States Semiquincentennial is the name used for the federal celebration and its organizing commission.

The terminology can be confused with better-known anniversary words. A bicentennial is a 200th anniversary, a sesquicentennial is a 150th anniversary, and a tricentennial is a 300th anniversary. America250 therefore uses a less familiar but mathematically precise label.