biannual

adjective

bi·​an·​nu·​al (ˌ)bī-ˈan-yə(-wə)l 

1

: occurring twice a year

2

: biennial sense 1

biannually 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?

When we describe something as biannual, we can mean either that it occurs twice a year or that it occurs once every two years. So how does someone know which particular meaning we have in mind? Well, unless we provide them with a contextual clue, they don’t. Some people prefer to use semiannual to refer to something that occurs twice a year, reserving biannual for things that occur once every two years. This practice is hardly universal among English speakers, however, and biannual remains a potentially ambiguous word. Fortunately, English also provides us with biennial, a word that specifically refers to something that occurs every two years or that lasts or continues for two years.

Examples of biannual in a Sentence

Politicians still tremble when Barry begins his biannual comeback flirtations.  … But if they'd spent less time looking over their shoulders and more time looking over election returns, they'd have seen that Barry was likely heading for a poleaxing when he called it quits. —Michael Schaffer, New Republic, 22 Apr. 2002

… have recommended routine annual or biannual mammographic screening for asymptomatic women without a personal or family history of breast cancer, starting at the age of 40. —Nels Marcus Thygeson, Journal of the American Medical Association, 8 July 1986

One of the more fascinating commonplace facts about the whitetail is its biannual change of color. Summer, when deer come "into the red," as the saying goes, scant reddish-brown hairs replace the winter coat. Fall, deer come back "into the blue," though less than blue, with a thick pelage of hollow, grayish-tan hairs … —John G. Mitchell, Smithsonian, November 1982

The group holds biannual meetings in December and July.

The art show is a biannual event that won't happen again for two more years.

Recent Examples on the Web

The foundation hosts biannual congresses, with panels devoted to discussing recent threats to the rule of law, and awarding honors to lawyers who defend it. —Fabio Bertoni, New Yorker, 25 Oct. 2025

They should have been gone on day one, which conveniently coincided with their council’s statutory biannual review and renewal, neither of which appears to have been conducted. —Paul Du Quenoy, MSNBC Newsweek, 24 Oct. 2025

The biannual time shift tends to affect peoples’ circadian rhythms — the body’s 24-hour clock — which regulate several physiological processes. —Hannah Poukish, Sacbee.com, 22 Oct. 2025

New York Men’s Day is a biannual showcase for emerging men’s and genderless brands. —Jean E. Palmieri, Footwear News, 17 Oct. 2025

Word History

First Known Use

1877, in the meaning defined at sense 1

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Kids Definition

biannual

adjective

bi·​an·​nu·​al (ˈ)bī-ˈan-yə(-wə)l 

: occurring twice a year

biannually

-ē

adverb