What term means a 250th anniversary, as in the United States’ America250 celebration?

Semiquincentennial is the term for a 250th anniversary, as in the United States’ America250 celebration.

The word combines “semi,” meaning half, with “quincentennial,” meaning a 500th anniversary. Together, the parts describe half of five centuries, or 250 years. The term is used for the United States’ 2026 anniversary of the Declaration of Independence.

Other labels have also appeared in historical and popular usage, including quarter millennium, sestercentennial, and bisesquicentennial. Semiquincentennial is the formal term most closely associated with the national commemoration and the United States Semiquincentennial Commission.

The word is easy to confuse with bicentennial, which means 200 years, and sesquicentennial, which means 150 years. Tricentennial means 300 years. America250 uses the number 250 as a simpler public name, while semiquincentennial supplies the specialized anniversary vocabulary.