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

Design Doha, a biennial event emerged on the international calendar in 2024 and Amman Design Week will return for its fourth edition in October 2026. —Sofia Celeste, Footwear News, 30 Oct. 2025

In 2019, as thousands of ministers gathered in Orlando, Florida, for the General Council’s biennial meeting, Jay Herndon, secretary-treasurer of the Northern California-Nevada district, introduced a resolution to protect children. —Mike Hixenbaugh, NBC news, 30 Oct. 2025

The group will discuss releasing $15 million set aside in the biennial budget passed earlier this year to begin planning the overhaul process. —Laura Schulte, jsonline.com, 27 Oct. 2025

As the inaugural biennial edition, LagosPhoto 2025 opens a transformative new chapter—building on fifteen years of experimentation while pursuing fresh dialogues around invention, resistance, and freedom. —Photovogue, Vogue, 25 Oct. 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