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[bahy-en-ee-uh l] /baɪˈɛn i əl/
adjective, Also, biyearly (for defs 1, 2).
happening every two years:
biennial games.
lasting or enduring for two years:
a biennial life cycle.
Botany. completing its normal term of life in two years, flowering and fruiting the second year, as beets or winter wheat.
any event occurring once in two years.
Botany. a biennial plant.
Origin of biennial
1615-25; bienni(um) + -al1
Related forms
biennially, adverb
Can be confused
biannual, biennial, semiannual (see usage note at bi-)
Usage note
See bi-1. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for biennial
  • No other team has won the biennial tournament three consecutive times.
  • Apparently, most varieties are perennial, but there are a few that are annual or even biennial.
  • The Americans have won seven consecutive matches in the biennial competition.
  • The biennial beet is often used in crop rotation.
  • Culture vultures descend on Venice for the city's biennial art fair.
  • The huge, biennial event dates back to 1924, when radio was introduced to German retailers as a hot new thing.
  • Since its inception the Academy, a notably conservative body, has maintained biennial.
  • Wordy types enjoy a night on the tiles at the biennial Scrabble world championship.
  • There's a biennial conference that I usually try to go to.
  • The biennial competition ends Sunday with 12 singles matches.
British Dictionary definitions for biennial


occurring every two years
lasting two years Compare biannual
a plant, such as the carrot, that completes its life cycle within two years, developing vegetative storage parts during the first year and flowering and fruiting in its second year Compare annual (sense 3), perennial (sense 3)
an event that takes place every two years
Derived Forms
biennially, adverb
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for biennial

"lasting for two years" (1620s); "occurring every two years" (1750), from Latin biennium "two-year period," from bi- (see bi-) + annus "year" (see annual). The vowel change is "due to the Latin phonetic law according to which the unaccented and closed radical syllable of the second element of compounds, original -ă- becomes -ĕ-" [Klein]. The noun meaning "a biennial plant" is attested by 1770.

Online Etymology Dictionary, © 2010 Douglas Harper
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biennial in Science
Adjective  Completing a life cycle normally in two growing seasons.

Noun  A biennial plant. In the first year, biennials normally produce a short stem, a rosette of leaves, and a fleshy root that acts as food supply. In the second season, biennials blossom, produce seed, use up their food supply, and die. Carrots, parsnips, and sugar beets are examples of biennials. Compare annual, perennial.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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