quincentennium

== English == === Etymology === From New Latin quincentennium (“500-year period”). Compare the classical Latin form quingenti (“500”). Equivalent to quin- (“five”) +‎ centennium (“century, 100-year period”). Cognate with quincentenary and quincentennial. === Noun === quincentennium (plural quincentennia) (rare) A period of five hundred years, half a millennium. Coordinate terms: annum, biennium, triennium, quadrennium, quinquennium, sexennium, septennium, octennium, novennium, decennium, vicennium, tricennium, centennium, millennium, decamillennium, centimillennium, millionennium === References === “quincentennial, adj. and n.”, in OED Online ⁠, Oxford: Oxford University Press, 2022.