Biannually vs Biennially. Are These Words Different?

Biannually vs Biennially. These words aren’t technically homophones, yet they are similar. Due to their similar spellings, meanings, and pronunciations, many writers often mix them up. So, what do these words mean? And is it correct to use them interchangeably? 

What Is The Meaning Of “Biannual?” 

Biannual” is a term that means “two times within a year.” It has clear Latin roots such as “annus” (year) and “bi” (two). Common English speech is used as an adjective to describe things that happen twice a year. For example: 

  • I can’t wait to go to the biannual business writing conference! 
  • We are getting closer to the biannual solstice. 

Generally, “biannual” refers to an event or a season. When used as an adverb, “biannual” becomes “biannually.” For instance: 

  • I go to my vacation home biannually in the fall and spring. 
  • I am fairly sure that my dentist appointments are scheduled biannually. 

As you can see in these examples, “biannually” describes how often the actions take place in a year. 

What Is The Meaning Of “Biennial?” 

Biennial” is a term that means “happening every two years.” Compared to “biannually,” which means it happens twice a year, “biennially” occurs less often, every two years. For example: 

  • Plants such as celery and carrots are biennial, as they flower and create seeds every two years. 
  • I try to plan a biennial trip to Asia to visit family. 
  • Even though it may sound odd, my job works on a biennial basis, meaning I must renew my contract and working agreements every two years. 

Biannually vs Biennially: What’s The Difference?

One great thing about distinguishing these two words is that they have a single distinct meaning that is hard to confuse. In other words, “biannual” and “biennial” both mean one specific thing, whereas words like “biweekly” and “bimonthly” can be interpreted in two different ways.  

To sum up the differences, “biannual” means that an action occurs more frequently, as it happens twice yearly. In contrast, “biennial” means that action occurs less frequently, as it happens every two years. One trick to try and remember these is to think of the root “annual” that appears in “biannual,” hinting that the actions occur within a single year. 


Are there people thinking about scaling [up] those innovations?” Interviewed ahead of next week’s biannual World Bank meeting, Kim added: “They [the climate change community] kept saying, ‘What do you mean a plan?’ I said a plan that’s equal to the challenge. – The Guardian

According to the UN’s latest biennial population forecast, the median age for all countries is due to rise from 29 now to 38 by 2050. – The Economist

Related: The Difference Between Bi and Semi

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By Ryan Fisher

Ryan holds degrees from Pacific Lutheran University and specializes in proofreading, editing, and content writing with an emphasis on business communication.

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