biannual

bi- +‎ annual.

• (Received Pronunciation) IPA^(key): /bʌɪˈanjuːəl/
• (General American) IPA^(key): /baɪˈænjuəl/

• Audio (AU)

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• Hyphenation: bi‧an‧nu‧al

biannual (not comparable)

1. Occurring twice a year; semiannual.
   • 1980, J[ose] D. Salas, J. W. Delleur, V. Yevjevich, W. L. Lane, Applied Modeling of Hydrologic Time Series, Littleton, Colo.: Water Resources Publication, →ISBN, section 8.9, page 448:

     The annual values were disaggregated into biannual values. Then the biannual values were disaggregated into quarterly values. Finally the quarterly values were disaggregated into the desired monthly values.

   • 1989, “Introduction”, in Ursula Schneider, Michael Schratz, editors, Permanent Education Between New Illiteracy and High Power Technology: 1988 Biannual Symposia, New Orleans, La.: Institute for the Comparative Study of Public Policy, University of New Orleans, →ISBN:

     Collection of papers presented at the workshops during the 1988 biannual symposia in February (New Orleans) and May (Innsbruck).

   • 1992, Simon J. Nuttall, European Political Co-operation, Oxford: Clarendon Press, →ISBN, page 286:

     […] the biannual meetings between the President of the European Council and the President of the United States were formalized, there were to be two meetings per year […]

   • 2007 August 9, “Biannual Newsletter”, in Royal College of Nursing‎, archived from the original on 30 October 2009:

     Biannual newsletter / The Society publishes a twice yearly newsletter, called "Headlines".

   • 2009, Jack P. Friedman, Jack C. Harris, Barry A. Diskin, Real Estate Handbook, 7th edition, Hauppage, N.Y.: Barron's Educational Series, →ISBN, page 163:

     Under a lease, Abel is required to make biannual rent payments, one in January and one in July […].

2. (proscribed) Occurring once every two years; biennial.
   • 1993, Agriculture: An Investment in Peace (Developing the Occupied Territories; 4), Washington, D.C.: World Bank Publications, →ISBN, page 1:

     The relative share of agriculture in GDP of the West Bank (calculated on the basis of fixed 1986 prices, and as a two-year average to deal with the major biannual fluctuations in olive production) declined […].

   • 1997, Steven Blakemore, Intertextual War: Edmund Burke and the French Revolution in the Writings of Mary Wollstonecraft, Thomas Paine, and James Mackintosh, Madison, N.J.: Fairleigh Dickinson University Press, →ISBN, pages 190–192:

     Thus he argues that the members of the National Assembly were independent from the constituencies that elected them, because the latter (the assemblies, administrative and elected) are "biennially renewed," as was the National Assembly. […] This [being responsible to electors] is implicitly the case of the representatives in the National Assembly, who must also face biannual elections […].

   • 2001, Kenneth I. Wolpin, Empirical Methods for the Study of Labor Force Dynamics (Fundamentals of Pure and Applied Economics; 60), Routledge, →ISBN, page 84:

     Now, after having solved the biannual period problem back to period one of the ten biannual periods, i.e. quarters 77–84 it is necessary to convert the state variables, namely n, SK and GK, from biannual to annual units.

   • 2004, Lee Penn, “The Earth Charter”, in False Dawn: The United Religions Initiative, Globalism, and the Quest for a One-world Religion, Hillsdale, N.Y.: Sophia Perennis, →ISBN, page 380, footnote 5:

     "The Earth Charter opens a new phase […]." (Mikhail Gorbachev, as quoted in The Earth Charter Initiative, Biannual Report 2002–2003, Earth Charter International Secretariat, http://www.earthcharter.org/files/resources/Biannual%20Report.pdf, p 10, […]).

Although biannual conventionally means twice a year, its conflation with biennial (once every two years) is quite common (among both readers and writers), leading to usage advice that it is better to write either semiannual or biennial (whichever is meant), or even more clearly, to write either twice a year or once every two years, than to write biannual at all.

• bi-annual

• (two times per year): half-yearly, semiannual, twice-yearly
• (every two years): biennial

• biannually

biannual (plural biannuals)

1. Something occurring twice each year.
   • 1995, Tamkang Review, volume 36, Taipei: Graduate School of Western Languages and Literature, Tamkang University, →ISSN, →OCLC, page 366:

     It was a biannual from April 1970 to October 1977 and has been a quarterly since fall 1978.