quadrennium

From Late Latin quadrennium, from Latin quadriennium, from quadriennis (“4-year”) + -ium (suffix forming abstract nouns).

• (General American) IPA^(key): /kwɑˈdrɛniəm/
• (Received Pronunciation) IPA^(key): /kwɒˈdrɛnɪəm/, /kwəˈdrɛnɪəm/

quadrennium (plural quadrenniums or quadrennia)

1. A period of 4 years, particularly (historical) the sets of four years in the ancient Egyptian and Greek calendars.

   Coordinate terms: annum, biennium, triennium, quinquennium, sexennium, septennium, octennium, novennium, decennium, vicennium, tricennium, centennium, quincentennium, millennium, decamillennium, centimillennium, millionennium

• tetraeteris, tetraeterid, olympiad

• See Thesaurus:quartet

• (adj.) quadrennial

• “quadrennium, n.”, in OED Online ⁠, Oxford: Oxford University Press, 2022.