‘Biannual’ vs. ‘Biennial’: Differences Between ‘Biannual’ and ‘Biennial’

“Biannual” means occurring twice in one year. Like many words in the English language, “biannual” is a word where the key to its etymology is in its Latin roots: The prefix “bi” means “two,” and “annus” means “year.” The word “biannual” is commonly used as an adjective describing occasions that happen twice a year: biannual events, biannual conferences, biannual solstices (summer and winter). “Biannual” is one of the more commonly confused English words.

Use the word “biannual” to describe an event or as a marker of time:

• “We live in Michigan, but we go to New York City biannually.” In this sentence, “biannually” is an adverb that shows that even though the speakers live states away, they make the trek to New York twice a year.
• “I work from home, but I go into the office for biannual in-person meetings.” Here, the speaker notes that they have to head into the workspace twice a year as a job requirement.
• “Her biannual parties—around Christmas and Memorial Day—are not to be missed.” The context clues in this sentence (listing two holidays) help clarify the meaning of “biannual,” which describes the frequency with which the host throws parties.

“Biennial” means happening once every two years. Cleaning your closet “biennially” means over two years you only do it once. If you clean out your closet “biannually,” you are doing it four times more often than you would if doing so “biennially.”

Learn how to use “biennial” correctly by studying these example sentences:

• “If your biennial plants didn’t flower this year, they should bloom next year.” The given information tells us that the biennial flowers in this sentence have a life cycle where they’ll bloom every other year.
• “We travel to Europe biennially, seeing a different country every time we go.” The speakers here have a biennial tradition of heading to Europe every two years. In this example sentence, “biennially” serves as an adverb to modify how often they travel.
• “He used to switch jobs biennially, but now he does so biannually.” In this sentence, we get two different markers of time: biennially and biannually. The person discussed has gone from changing jobs once every other year to doing so twice a year.

“Biannual” and “biennial” have more precise meanings than words like “bimonthly” and “biweekly.” “Biweekly” can mean occurring every other week or occurring twice a week; the same goes for “bimonthly” in months. Biannual and biennial, meanwhile, have separate meanings.

“Biannual” means occurring twice in one year, and “biennial” means happening once every two years. Think of “biannual” as synonymous with “semiannual”: both mean happening twice a year. A trick for remembering “biennial” is to think of the Venice Biennale’s fine art and architecture exhibits—a famous, international art event—which takes place every other year. Both words have Latin roots and can be adjectives; biennial can also be a noun. They are both commonly used as adverbs, such as “biannually” and “biennially.”

Become a better writer with the MasterClass Annual Membership. Gain access to exclusive video lessons taught by the world’s best, including James Patterson, Neil Gaiman, Walter Mosley, Margaret Atwood, Joyce Carol Oates, Dan Brown, and more.