Biannual vs. Semiannual – What’s the Difference?

Sometimes, English has more than one word that refers to the same idea. Other times, very similar words will refer to different ideas, introducing confusion.

That is the case with the words biannual and biennial, which appear nearly identical, but do not mean the same thing. Biannual carries the same meaning as semiannual, but what does biennial mean? Continue reading to find out.

What is the Difference Between Biannual and Semiannual?

In this article, I will clarify biannual vs. semiannual; as part of the discussion, I will include several examples of each word in a sentence to demonstrate its use in context.

I will also show you a memory tool that you can use next time you can’t remember whether you’re describing something that is biannual or semiannual.

When to Use Biannual

biannual versus semiannual meaningWhat does biannual mean? Biannual is an adjective that specifies the frequency of occurrence. Something that is biannual happens twice a year.

Here are a few example sentences,

  • Equinoxes are biannual; one happens in March and in September.
  • If birthdays were biannual, humans would age twice as fast.
  • “Isn’t it about time for Todd and Sharon’s biannual breakup?” Sven asked, looking at the calendar.
  • Yellen was invited to Capitol Hill to deliver a biannual report on monetary policy to the Senate Banking Committee. –The New York Times

When to Use Semiannual

Definition of semiannual definition and definition of biannual definitionWhat does semiannual mean? Semiannual is also an adjective, and it also describes something that happens twice a year.

Here are some examples,

  • The finance department undertakes a semiannual full audit of all company expenses.
  • Semiannual raises boost employee morale, but also eat up profits.
  • The semiannual campus bacchanalia usually, but not always, occurs after semester finals are over.
  • Federal Reserve Chairwoman Janet Yellen will deliver her semiannual monetary policy report to the Senate Banking Committee on Feb. 14, a panel spokeswoman confirmed Friday. –The Wall Street Journal

I’m not sure what word came first, semiannual or biannual, but, in the modern day, most people use semiannual to avoid any confusion that arises from biannual vs. biennial.

When to Use Biennial

Define semiannual and define biannualWhat does biennial mean? A third adjective, biennial, describes something that occurs every other year. This term is often confused with biannual due to their similarity in spelling.

Here are some examples of biennial in a sentence,

  • The San Francisco Giants had to forgo their biennial trip to the World Series in 2016.
  • The biennial congressional elections in America often give the illusion of hope for the minority party.
  • I visited two years ago, when Montrose hosted the Fête de la Fleur, a black-tie gala during the biennial Vinexpo trade fair. –The Washington Post

Trick to Remember the Difference

These words are so similar that it’s easy to confuse them in your writing. To avoid inadvertently misleading your readership, you should strive to write as clearly as possible.

To this end, best practice is to write around the confusion introduced by these terms. Use semiannual to refer to things which happen twice a year. Since biannual and biennial are the real problem, writer Bryan Garner (2016) recommends that you avoid them entirely, and use every other year instead.

Since the prefix semi- refers to half or part or something, you can use it to remind yourself that something that is semiannual only goes part of a year before happening again.

If, however, you want to keep using biannual and biennial, here is a trick to remember the difference. You can think of the “E” in biennial as standing for “every other year.”


Is it biannual or semiannual? Biannual, biennial, and semiannual are adjectives that describe the frequency at which events occur.

  • Biannual and semiannual mean twice a year.
  • Biennial means every other year.

For the sake of clarity, it would be best to avoid all of these terms and simply write twice a year or every other year. However, writers must balance clarity with concision, making semiannual a useful choice for something that happens at that frequency.

Since semi- means half or part, it will be easy to remember that you only need to wait part of a year before something semiannual happens again.