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

With the Nurburgring dropping out of the calendar, the race was held at Hockenheim on a biennial basis until its final edition in 2019. —Dan Cancian, Forbes.com, 15 May 2025

Talking about the biennial event at every opportunity comes with the job, and the American team captain knows it. —Julio Cesar Valdera Morales, MSNBC Newsweek, 14 May 2025

The genus Gaillardia includes annual, perennial, and biennial species, all of which perform beautifully in mixed borders, cottage gardens, or meadow plantings. —Kim Toscano, Southern Living, 6 Apr. 2025

The railroad is also seeking state assistance as the Indiana General Assembly drafts its biennial budget this month. —Doug Ross, Chicago Tribune, 1 Apr. 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