What term names a 250th anniversary such as America's America250 celebration?
Answer
Semiquincentennial
A 250th anniversary such as America's America250 celebration is called a semiquincentennial.
The word combines semi-, meaning half, with quincentennial, a 500-year anniversary. Half of 500 years is 250 years, giving the term its basic construction. The United States uses “United States Semiquincentennial” as a formal name for the 2026 commemoration.
Several alternative terms exist. Sestercentennial, bisesquicentennial, quarter millennium, and bicenquinquagenary have all been used or proposed for a 250-year anniversary. Semiquincentennial is the term most directly associated with the national 2026 observance and the America250 branding.
The number-based names can be confused with better-known anniversary words. A bicentennial is 200 years, a sesquicentennial is 150 years, and a tricentennial is 300 years. America250 is therefore a semiquincentennial, not a bicentennial.