What term names the 250th anniversary being celebrated by the United States Semiquincentennial?

The term for the 250th anniversary being celebrated by the United States is semiquincentennial.

The word combines “semi,” meaning half, with “quincentennial,” relating to 500 years. Together, the term describes half of a 500-year anniversary, or 250 years. It is the name used for the United States' 2026 anniversary and appears in the formal title United States Semiquincentennial.

Several less familiar alternatives also exist. Sestercentennial and bisesquicentennial are used as synonyms, while quarter millennium is a plain-language description. These alternatives can create confusion, but America250's official branding generally uses the shorter “America250” name.

The numerical prefixes distinguish this anniversary from earlier celebrations. Centennial means 100 years, sesquicentennial means 150, and bicentennial means 200. The United States celebrated its bicentennial in 1976, exactly half a century before the 2026 semiquincentennial.