Biannual vs. Biennial: Comparing the Frequency and Meanings

, Staff Writer
Updated November 15, 2021
Biannual - Annual calendar, clock and pen vs Biennial - Voter voting in polling place
    Biannual - Annual calendar, clock and pen vs Biennial - Voter voting in polling place
    Calendar: Pinopic / E+ / Getty Images / Voter: Hill Street Studios / DigitalVision / Getty Images
    Used under Getty Images license

You receive an invitation to a biannual event, but wait: Does that mean you’ll be invited again in six months, or will you have to wait two years? Or is that biennial? One of these words means one thing, and one the other, but which is it?

Comparing the Meanings of Biannual and Biennial

While only two letters separate biannual and biennial, the difference in time is much bigger. The prefix bi- means two, so whenever you see bi- you know you are dealing with something that occurs twice.

  • biannual - twice a year

  • biennial - every two years

How to Use Biannual in a Sentence

Annual is a word of Latin origin that means “yearly” or “occurring every year,” so biannual means “twice yearly.”

  • I’m a contributing writer for a biannual journal.

  • You should schedule your biannual dentist appointment.

  • Our biannual meeting is on Thursday.


Biennial Meaning and Usage

The Latin term ennial means “yearly.” Therefore, biennial means “every two years” or “every other year.”

  • Senators are up for election biennially.

  • Preparations are underway for the biennial event.

  • They reviewed the biennial budget.

What About Other Bi- Words?

In addition to biannual and biennial, there are several other bi- terms like biweekly, bimonthly and biyearly. This can get confusing because depending on the context, bi- in these instances can mean “every two” or “occurring twice.”

  • biweekly - twice a week or every two weeks

  • bimonthly - twice a month or every two months

  • biyearly - twice a year or every two years

How to Remember the Difference

Biannual and biennial are understandably easy to mix up. They look and sound similar; they have the same prefix, and they only differ by two letters. A good way to remember their respective meanings is that ennial and every both begin with “e,” so you can associate that with “every other year.” Additionally, annual begins with an “a” and means “yearly.” You can also associate annual with “anniversary,” which is something that occurs once a year and also begins with an “a.”


Always Choose the Correct Word

Now that you have mastered the meanings of biannual and biennial, discover the difference between biannual and semiannual. Then review other words that look similar but have different meanings, such as inter and intra.