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?
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
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.
Suzanne Blake, MSNBC Newsweek, 13 June 2025
Both companies have committed to releasing new AI chips on an annual basis, as opposed to a biannual basis, emphasizing how fierce competition has become and how important bleeding-edge AI chip technology is for companies like Microsoft, Oracle and Amazon.
—Kif Leswing, CNBC, 12 June 2025
According to the Nation’s Report Card, a biannual assessment of math and reading administered to students in every state, Illinois needs to commit to more rigorous standards, not weaken them.
—Bruce Rauner, Chicago Tribune, 8 June 2025
Even brief, biannual updates can highlight the positive impact of security initiatives across various parts of the business.
—Chaim Mazal, Forbes.com, 17 June 2025
See All Example Sentences for biannual
Cite this Entry
“Biannual.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/biannual. Accessed 9 Jul. 2025.
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