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

Usage of Bimonthly

Bimonthly and biweekly are inherently ambiguous because bi- can mean both "occurring every two" and "occurring two times." This ambiguity cannot be eliminated by the dictionary. If you need bimonthly or biweekly, we suggest leaving some clues in your context about which sense of bi- you intend. Note that if you need the meaning "twice a," you can also substitute semi- for bi- without additional clarification: semimonthly, semiweekly. Dealing with years is generally simpler: biannual usually means "occurring twice a year" and biennial usually means "occurring every two years."

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

Analysts say the biennial auto show in China's capital, which opened to media on Friday, shows how its auto industry is setting the global pace for cutting-edge technologies in areas such as electric vehicles and batteries, eclipsing many foreign brands that used to dominate the global market. —ABC News, 24 Apr. 2026

With Yina Jiménez Suriel, Fonseca will codirect the 2027 edition of Rejkjavík’s biennial Sequences festival. —News Desk, Artforum, 22 Apr. 2026

Against that backdrop, The Bennett Prize — a biennial award for women painters working in figurative realism — just raised its grand prize from $50,000 to $75,000. —The Editors Of Artnews, ARTnews.com, 14 Apr. 2026

Benninger offered demographic insights as part of an update on the agency’s NWI 2050+ comprehensive plan, which is undergoing a biennial update. —Doug Ross, Chicago Tribune, 12 Apr. 2026

Word History

First Known Use

1562, in the meaning defined at sense 1

Rhymes for biennial

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