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

Many gardeners enjoy starting lettuce or carrots by seed outdoors, but few of us start perennial or biennial flowers by seed. —Henry Homeyer, The Providence Journal, 13 Mar. 2026

Hosted every two years by the Whitney Museum of American Art in New York, this year’s biennial features 56 artists and collectives, roughly 1 in 6 of whom have lived and worked in Los Angeles in the time since the survey’s last iteration. —Grant Klarich Johnson, Los Angeles Times, 10 Mar. 2026

Some are perennial, while others have an annual or biennial lifecycle. —Kim Toscano, Southern Living, 8 Mar. 2026

Underly made her $45 million request during the 2025-27 biennial budget process. —Miranda Dunlap, jsonline.com, 6 Mar. 2026

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