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The cafeteria at the 2017 Venice Biennale. This international art exhibition is held every biennium.

From Latin biennium, from biennis (2-year) + -ium (forming abstract nouns), from bi- (two) + annus (year), q.v.



biennium (plural bienniums or biennia)

  1. A period of two years, particularly for purposes involving intercalation or fiscal calculations.
    Coordinate terms: annum, triennium, quadrennium, quinquennium, sexennium, septennium, octennium, novennium, decennium, vicennium, tricennium, centennium, quincentennium, millennium, decamillennium, centimillennium, millionennium
    • 1704, Giles Strauchius [i.e., Aegidius Strauch II], “Of the Lunar Cycle”, in Richard Sault, transl., Breviarium Chronologicum. Or A Treatise Describing the Terms and Most Celebrated Characters, Periods and Epocha’s Used in Chronology. By Giles Strachius, D.D. and Publick Professor in the University of Wittebergh. Now Done into English from the Third Edition, in Latin. By Richard Sault, F.R.S., 2nd corr. and enl. edition, London: Printed for A. Bosvile at the Dial and Bible against St. Dunstan's Church in Fleet-street, →OCLC, book II (Of Chronological Characters), § 1, pages 93–94:
      The Greeks being taught by their Oracles, that their accuſtomed Sacrifices were to be offered κατά τρία, which they underſtood as if their Year were to be regulated by the Sun, and their Days and Months were to be adjuſted by the motion of the Moon; were always ſolicitous, how by certain Periods they might reduce the diſagreeing motions of the Luminaries to a Third ſomething in which they might agree: Hence in the ancient times they are ſaid to have uſed a Biennium, intercalating every other year: But fault was found with this, and 'twas ſucceeded by a Quadriennium; upon the return of which the Olympic Games were celebrated.
    • 1858, Herodotus, George Rawlinson and Henry Rawlinson, translators and editors, “The First Book, Entitled Clio”, in The History of Herodotus. A New English Version, Edited with Copious Notes and Appendices, Illustrating the History and Geography of Herodotus, from the Most Recent Sources of Information; and Embodying the Chief Results, Historical and Ethnographical, which have been Obtained in the Progress of Cuneiform and Hieroglyphical Discovery. [...] In Four Volumes, volume I, London: John Murray, Albemarle Street, →OCLC, footnote 2, page 178:
      No commentator on Herodotus has succeeded in explaining the curious mistake whereby the solar year is made to average 375 days. That Herodotus knew the true solar year was not 375, but more nearly 365 days, is clear from book ii. ch. iv. It is also clear that he must be right as to the fact that the Greeks were in the habit of intercalating a month every other year. This point is confirmed by a passage in Censorinus (De Die Natal. xviii. p. 91), where it is explained that the Greek years were alternately of 12 and 13 months, and that the biennium was called "annus magnus," or τριετηρίς.
    • 2007, Digambar Bhouraskar, “Growth and Structure of EPTA [Expanded Programme of Technical Assistance]”, in United Nations Development Aid: A Study in History and Politics, New Delhi: Academic Foundation, →ISBN, page 138:
      During the bienniums 1963–64 and 1965–66, expenditure on regional and inter-regional projects also registered a substantial growth. In fact, the share of regional projects in the total programme during the bienniums 1963–64 and 1965–66 was higher than the 12 per cent deemed desirable by the TAC [Technical Assistance Committee].
    • 2014, Joel W. Paddock, “Local and State Political Parties”, in Donald P. Haider-Markel, editor, The Oxford Handbook of State and Local Government, Oxford: Oxford University Press, →ISBN, page 231:
      Although ideology is related to the propensity for a state to adopt stringent changes to campaign finance law, culture does not have a substantive effect. However, he [Christopher Witko] finds support that a scandal in the previous biennium is associated with changes to campaign finance regulation in the current biennium, in concert with the findings of [Beth] Rosenson (2005) on the adoption of legislative ethics reforms.
    • 2016, Manabu Saeki, “Ideology of Partisan Voters and Congressional Members”, in The Phantom of a Polarized America: Myths and Truths of an Ideological Divide, Albany, N.Y.: State University of New York Press, →ISBN, page 58:
      Ideology of Republican voters demonstrates a significant, if not enormous, rightward shift during this period. In contrast to Republican legislators, the conservative shifts by Republican voters betided in a few, rather than all, biennia, interrupted by other biennia with no ideological shift.

Derived terms[edit]





Etymology 1[edit]

From biennis (2-year) +‎ -ium (forming abstract nouns), from bi- (two) + annus (year), q.v.


biennium n (genitive bienniī or biennī); second declension

  1. biennium

Second-declension noun (neuter).

Case Singular Plural
Nominative biennium biennia
Genitive bienniī
Dative bienniō bienniīs
Accusative biennium biennia
Ablative bienniō bienniīs
Vocative biennium biennia

1Found in older Latin (until the Augustan Age).

  • Catalan: bienni
  • English: biennium
  • Italian: biennio
  • Romanian: bieniu
  • Spanish: bienio

Etymology 2[edit]

Regularly declined forms of biennis.



  1. genitive masculine/feminine/neuter plural of biennis


  • biennium”, in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
  • biennium”, in Charlton T. Lewis (1891) An Elementary Latin Dictionary, New York: Harper & Brothers
  • biennium in Charles du Fresne du Cange’s Glossarium Mediæ et Infimæ Latinitatis (augmented edition with additions by D. P. Carpenterius, Adelungius and others, edited by Léopold Favre, 1883–1887)
  • biennium in Gaffiot, Félix (1934) Dictionnaire illustré latin-français, Hachette.