What Greek-derived term names the 250th anniversary celebrated by the United States Semiquincentennial?

The Greek-derived term for the United States’ 250th anniversary is semiquincentennial.

The word combines “semi,” meaning half, with “quincentennial,” referring to a 500-year anniversary. Half of 500 years is 250 years, so semiquincentennial describes a 250th anniversary. The term is used for America250, the national commemoration of American independence.

Several other names have appeared in discussions of the anniversary, including sestercentennial, quarter millennium, and bisesquicentennial. Semiquincentennial is the formal title used for the United States celebration and its congressional commission.

The more familiar anniversary terms can cause confusion. A bicentennial marks 200 years, a sesquicentennial marks 150 years, and a tricentennial marks 300 years. The 2026 observance is therefore not a bicentennial or tricentennial, but a semiquincentennial.