bicentennial adj.

word-forming element meaning "two, having two, twice, double, doubly, twofold, once every two," etc., from Latin bi- "twice, double," from Old Latin dvi- (cognate with Sanskrit dvi-, Greek di-, dis-, Old English twi-, German zwei- "twice, double"), from PIE root *dwo- "two."

Nativized from 16c. Occasionally bin- before vowels; this form originated in French, not Latin, and might be partly based on or influenced by Latin bini "twofold" (see binary). In chemical terms, it denotes two parts or equivalents of the substance referred to. Cognate with twi- and di- (1).

"consisting of or lasting 100 years, happening every 100 years," 1789, from Latin centum "one hundred" (see hundred) + ending from biennial. As a noun, "a hundredth anniversary celebration," from 1876; the older noun is centenary.

"pertaining to a 200-year period," 1843; see bi- + centenary. Also see bicentennial. As a noun, "two-hundredth anniversary or celebration," from 1840.