biennial

adjective

bi·​en·​ni·​al (ˌ)bī-ˈe-nē-əl 

1

: occurring every two years

a biennial celebration

2

: continuing or lasting for two years

specifically, of a plant : growing vegetatively during the first year and fruiting and dying during the second

Biennial herbs flower in their second year.

biennial noun

biennially

(ˌ)bī-ˈe-nē-ə-lē 

adverb

What do bimonthly and biweekly mean?: Usage Guide

Many people are puzzled about bimonthly and biweekly, which are often ambiguous because they are formed from two different senses of bi-: "occurring every two" and "occurring two times." This ambiguity has been in existence for nearly a century and a half and cannot be eliminated by the dictionary. The chief difficulty is that many users of these words assume that others know exactly what they mean, and they do not bother to make their context clear. So if you need bimonthly or biweekly, you should leave some clues in your context to the sense of bi- you mean. And if you need the meaning "twice a," you can substitute semi- for bi-. Biannual and biennial are usually differentiated.

Did you know?

Biennial conventions, celebrations, competitions, and sports events come every two years. Biennials are plants that live two years, bearing flowers and fruit only in the second year. (Carrots and sugar beets are two examples; since we're only interested in their roots, we don't wait another year to see their flower and fruit.) In contrast, semiannual means "twice a year". But no one can agree whether biweekly means "twice a week" or "every two weeks", and whether bimonthly means "twice a month" or "every two months". Maybe we should stop using both of them until we can decide.

Examples of biennial in a Sentence

The governor explained the biennial budget proposal.

Recent Examples on the Web

Despite representing the red, white and blue on consecutive teams at the prestigious biennial team event, Bradley was on the outside looking in as the Ryder Cup marched on in 2016, 2018 and 2021—the latter event postponed a year due to the Covid-19 pandemic. —Michael Loré, Forbes.com, 20 Aug. 2025

In Indiana, the legislature approved a biennial budget that eliminated all funding to Indiana PBS and NPR stations. —Alexandra Kukulka, Chicago Tribune, 19 Aug. 2025

Then the volunteers and their generative agents took the General Social Survey, a biennial questionnaire that has cataloged American public opinion since 1972. —Webb Wright, Scientific American, 18 Aug. 2025

Taking place at the historic Bethpage Black Golf Course in Farmingdale, the 45th Ryder Cup will see the U.S. face off against Europe in the biennial men’s golf tournament from September 26 to 28. —Rachel Cormack, Robb Report, 18 Aug. 2025

Word History

First Known Use

1562, in the meaning defined at sense 1

Rhymes for biennial

• centennial
• decennial
• millennial
• perennial
• quadrennial
• quinquennial
• triennial
• bicentennial
• sesquicentennial

Kids Definition

biennial

adjective

bi·​en·​ni·​al (ˈ)bī-ˈen-ē-əl 

1

: occurring every two years

2

: growing stalks and leaves one year and flowers and fruit the next before dying

biennial noun

biennially

-ē-ə-lē 

adverb