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Biennial vs. Biannual: What's the Difference?

Edited by Janet White || By Harlon Moss || Updated on November 15, 2023
Biennial means every two years; biannual means twice a year.

Key Differences

Biennial and biannual are terms that describe the frequency of events, but they do so in distinct ways. The word biennial refers to something that occurs or is performed every two years. For instance, a biennial event is an event that takes place once every two years. On the other hand, biannual describes something that happens twice within a single year. It could be an event that takes place every six months or twice in a calendar year.
Both biennial and biannual have their roots in Latin. The prefix "bi-" means two, but the difference lies in the latter part of each word. In biennial, "enn" comes from the Latin word "annus" which means "year." Hence, when combined, it signifies "every two years." In contrast, biannual contains the word "annual," which refers to something that is yearly. When "bi-" is prefixed to "annual," it denotes "twice a year."
It's essential to be clear with these terms, especially in professional settings. For example, a biennial conference means attendees would gather once every two years. In contrast, a biannual meeting implies that members would meet twice within one year. Mixing these up can lead to confusion about scheduling and frequency.
In daily usage, people might unintentionally interchange biennial and biannual, but their meanings are distinct. To differentiate, one can associate biennial with "lengthier intervals" (every two years) and biannual with "more frequent occurrences" (twice a year).

Comparison Chart


Occurs every two years
Occurs twice a year


"bi-" + "enn" from "annus" (year)
"bi-" + "annual" (yearly)


Biennial plant
Biannual report


Less frequent (once in two years)
More frequent (twice in one year)


Longer interval between occurrences
Shorter interval between occurrences

Biennial and Biannual Definitions


Lasting for a period of two years.
The biennial budget was approved after extensive discussions.


Happening twice a year.
The biannual sale is the best time to grab deals.


Relating to a two-year term.
The senator served a biennial term before seeking reelection.


Twice yearly or semiyearly.
Subscriptions to the magazine are biannual.


An event taking place every two years.
The biennial conference is a must-attend for professionals in the field.


Semiannual; occurring or produced twice a year.
The company's biannual report showed significant growth.


Occurring every two years.
The biennial art exhibition attracts artists worldwide.


Occurring every six months.
The biannual checkup helps monitor health efficiently.


A plant that lives for two years.
Carrots are a biennial plant, producing seeds in their second year.


Pertaining to two distinct times in a year.
The biannual festivals are celebrated with much enthusiasm.


Happening every second year.


Occurring twice each year; semiannual.


(Botany) Having a life cycle that normally takes two growing seasons to complete.


Occurring every two years; biennial.


Occurring twice a year; semiannual.


(proscribed) Occurring once every two years; biennial.


Something occurring twice each year.


Occurring twice a year; half-yearly; semiannual.


Occurring or payable twice each year


Is there a difference between biennial and biannual plants?

Yes, biennial plants live for two years, while biannual plants don't exist in botanical terminology.

Is biannual the same as semi-annual?

Yes, biannual and semi-annual both mean twice a year.

Can plants be described as biennial?

Yes, biennial plants live for two years, flowering and producing seeds in the second year.

Does biennial mean every two years?

Yes, biennial means every two years.

How many times does a biannual event occur in one year?

A biannual event occurs twice in one year.

What's the root of the word biennial?

The root is "bi-" + "enn" from "annus" which means year.

Does biennial relate to longer durations than biannual?

Yes, biennial refers to every two years, whereas biannual refers to twice a year.

If a company releases a report in March and September, is it biennial or biannual?


Can a meeting be both biennial and biannual?

No. Biennial means every two years, while biannual means twice a year.

How often should I attend a biennial conference?

A biennial conference takes place every two years.

Is a biannual payment made twice a year or every two years?

A biannual payment is made twice a year.

Are there any other terms related to these that I should know?

Yes, "annual" means yearly, and "perennial" means lasting many years or recurring year after year.

How can I remember the difference between biennial and biannual?

Associate biennial with "lengthier intervals" and biannual with "more frequent occurrences."

Can both biennial and biannual refer to plants?

Biennial can describe plants, but biannual isn't used in botanical terms.

Which term describes an event that happens in January and July?


Which is more frequent: biennial or biannual?

Biannual is more frequent as it occurs twice a year, while biennial occurs every two years.

If a magazine is published in February and August, is it biennial or biannual?


Are these terms used internationally?

Yes, but clarity is essential as they can often be confused.

Do biennial plants die after two years?

Yes, biennial plants typically complete their lifecycle in two years.

Is it common for people to mix up biennial and biannual?

Yes, because of their similarity, they are often confused.
About Author
Written by
Harlon Moss
Harlon is a seasoned quality moderator and accomplished content writer for Difference Wiki. An alumnus of the prestigious University of California, he earned his degree in Computer Science. Leveraging his academic background, Harlon brings a meticulous and informed perspective to his work, ensuring content accuracy and excellence.
Edited by
Janet White
Janet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.

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