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Biennial or Biannual: Which is Correct?

Many people pronounce “biennial” and “biannual” similarly, confusing the listener as the speaker might mean something entirely different. Even when English language learners know there are differences between the two words, they often don’t know which is which and want to know whether to use “biennial” or “biannual.”

Both “biennial” and “biannual” are correct to use in the proper context. You use both words concerning time. “Biennial” refers to something that is happening once every two years. “Biannual” indicates that something is repeated twice in one year. We generally use them as adjectives, but they can also be adverbs, and “biennial” is often a noun.

We’ll discuss the use of the two words and in what contexts you can use them correctly. We’ll also look at the correct pronunciation of the words. Finally, to help you understand and remember the difference between the two words, we’ll end the article with references to different biannual and biennial events and reports.

The Meaning of Biannual and Biennial

To understand when and how to use “biannual” and “biennial” correctly, one has to know the meaning of each word.

What Does Biannual Mean?

Literally, biannual means “twice a year.” English speakers started to use the word biannual in the 1870s. It is a combination of the prefix  bi-, meaning “twice” or “two,” and the word annual, meaning “happening every year.”

It generally refers to an ongoing event or report repeated two times in a year, every year. But it can sometimes indicate something happening twice in one specific year only.

What Does Biennial Mean?

Nowadays, “biennial” means “once every two years.” The origin of the English word “biennial” was in the 1620s, meaning “lasting for two years.” This application originated from the Latin word “biennium,” meaning “two-year period.” However, as of 1750, English speakers have primarily used it for “occurring every two years.”

“Biennial” is also a noun that describes a plant that requires two seasons of growth before producing flowers and fruit. This meaning of the word has been in use since the 1770s (source).

How Do You Use Biannual?

Generally, “biannual” or “biannually” refers to an ongoing event or report that recurs twice a year, every year. For example, if the sports club presents two athletic tournaments twice a year and repeats the pattern every year, you refer to them as biannual events. 

But you can also use “biannual” when two similar events happen in one specific year only. For instance, if the human science faculty has decided to present two seminars on similar topics during 2021, you can refer to the second seminar as “the last biannual seminar of 2021.”

You can use “biannual” as an adjective describing the event as a noun or “biannually” as an adverb describing the activity as a verb.

Biannual as Adjective

You use biannual as an adjective before a noun, as in “The department has just released its biannual report.” “Biannual” describes the noun “report,” and the sentence means that the department provides two reports a year, and they have just released one of them.

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The following sentence also illustrates the use of the adjective: “This document is the tenth biannual review of the company’s sales.” Here “biannual” describes the noun “review” to convey the meaning that the company issues a review twice a year and has done it now for five years.

When the family is on their biannual holiday at the beach, it is one of two scheduled holidays they always have during a year, and you’ve used “biannual” to describe the noun “holiday.”

You will find that when biannual functions as an adjective, it primarily refers to scheduled events or reports. If you think about it, you can only label an event or report as “biannual” if you know it will occur twice during the year. 

Biannual as Adverb

You can also use “biannually” as an adverb when it is describing an action. However, often when “biannually” functions as an adverb, it is in the passive voice.

As an example, you can say that the office address list is updated biannually on January 1 and July 1. In this sentence, “biannually” describes the verb “updated,” indicating that someone updates the list twice a year.

Another passive voice example is “The children’s teeth are checked biannually by the dentist.” “Biannually” describes the verb “checked.” 

But you can also use it in the active voice. For example, an active voice sentence would be “He visits his doctor biannually.” Here, the subject performs the actions, and the adverb describes the verb “visits,” meaning he visits his doctor twice a year.

Thus, when you use “biannually” as an adverb and describe the action (verb) as a biannual action, it refers to an action someone does twice a year, every year.  

How Do You Use Biennial?

As in the case of “biannual,” you can use “biennial” as an adjective describing a noun or “biennially” as an adverb describing a verb. In some instances, you can also use “biennial” as a noun.

Biennial as Adjective

One can use “biennial” as an adjective with a noun. If the athlete takes part in a biennial sporting event in London, “biennial” describes the noun phrase “sporting event.” The sentence refers to a sporting event that occurs once every two years, and the athlete is now competing in one such event. 

In the following sentence, “biennial” is describing the type of prize (noun): “Two years ago, they rewarded Sarah with the city’s biennial Music Prize.” This means that the city offers a prize once every two years and Sarah has won the previous award.

Biennial events refer to events or reports scheduled to take place once every two years. 

Biennial as Adverb

The adverb “biennially” describes a verb, as in “The board elects a new chairman biennially.” “Biennially” is an adverb describing how the board elects its chairman — by holding elections every two years.

In the following sentence, “biennially” describes the verb “service”: “The company’s policy is that they must service all the computer stations biennially in February.” 

All this means is that someone in the company has to service the stations every second February.

Biennial as a Noun   

“Biennial” is also a noun. Many biennial events, especially art events, are just known as “The Biennial.” It is correct to say that after visiting the Biennial in Paris, you can see why artists want to exhibit there.

One finds another example of “biennial” as a noun in the flora environment. We might also call a plant that completes its life cycle in two growing seasons a biennial (source). 

Is It Correct to Hyphenate Biannual and Biennial? 

People learning English sometimes want to hyphenate biannual and biennial because the prefix ends on a vowel and the root word starts with a vowel. But let’s discuss whether this is correct.

Is Biannual Hyphenated?

You may wonder whether such a word as “bi-annual” exists and, if so, does the hyphen give another meaning to “biannual”? Although it might seem logical to hyphenate the word because of the vowels “i” and “a” next to each other, the hyphenation rules are simple.

You only hyphenate root words with prefixes to avoid word confusion, which is why you hyphenate a word where the root starts with an “i” and the prefix ends with an “i” like semi-independent. Again, the hyphen helps to avoid confusion.

With “biannual,” the spelling of the word doesn’t confuse you in any way when someone writes the prefix and root as one word. Thus, there is no reason to use the hyphenated prefix.

Is Biennial Hyphenated?

For the same reasons as we set out above, “biennial” is also not hyphenated. There is no confusion with the word when the prefix forms part of the root. Furthermore, -ennial has no specific meaning if you use it alone.

So it is clear that “bi-annual” and “bi-ennial” are incorrect spellings of the words “biannual” and “biennial,” which you might see if a person doesn’t understand hyphenating rules.

Are Biannual and Biennial Homophones?

Although there is a slight difference in the pronunciation of “biannual” and “biennial,” many speakers pronounce them similarly. Thus, some scholars view the two words as homophones — two words that sound the same but are different in meaning and spelling (source). 

How Do You Pronounce Biannual?  

When you write the word “biannual” phonetically, it becomes clear that the US and UK English pronunciations are the same. Merriam-Webster lists the correct pronunciation as \ (ˌ)bī-ˈan-yə(-wə)l\ while the Cambridge Dictionary lists the IPA format /baɪˈæn.ju.əl/ for American English and British English.

How Do You Pronounce Biennial?

As with “biannual,” the pronunciation of “biennial” is the same in UK and US English. The correct pronunciation is /baɪˈen.i.əl/ using the IPA system or \ (ˌ)bī-ˈe-nē-əl \ using Merriam-Webster’s system (source).

The Two Words are Not Interchangeable

Unfortunately, as they sound so similar, many people learning English incorrectly use the two words interchangeably, even when they write the words down.

As the “biannual” and “biennial” sound so similar but are not interchangeable, you must ensure that when you make a vocal presentation, for instance, the listener knows what word you are using. Misunderstanding can have far-reaching effects.

If you are doing a presentation about a franchise people can acquire, and the prospective franchisees understand that they have to pay a levy only biennially, it will be a big shock to them when they discover that they have to pay that levy biannually!

To avoid confusion when using one of the two words in writing or otherwise, it is a good idea to consider saying “once every two years” instead of “biennial” and “semiannual” when you mean “biannual” (source).

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Examples of Biannual and Biennial Events and Reports

A great number of diverse biennial and biannual events take place every year. Have a look at those we’ve listed here, and they will help you remember the difference between the meaning of biannual and biennial events. 

They will also help enforce that they are not interchangeable, although the two words are correct in their proper context.

Biannual Events and Reports

We are not always aware of how many biannual events and reports we encounter in our everyday life. For example, many schools have biannual parent-teacher meetings. 

If you have school-going children, you most probably attend their school’s biannual meetings at the beginning of the academic year and again before the final exams.

Many community-based organizations have biannual activities like charity fundraising markets. They commonly take place at the beginning of the summer holidays and again during the December festive season.

Most businesses and local authorities also publish biannual reports in May and November of each year.

Biennial Events and Reports

Biennial events are generally more renowned than biannual events. Some of the best-known and famous biennial events include La Biennale di Venezia, which is an art exhibition in Venice where more than 160 artists represent more than 100 countries every two years. The first Biennial was in 1895.

The Whitney Biennial is a favorite US art exhibition held every two years, although it was an annual event for a few years. This article was written for

There are also many biennial events outside the art environment. A good example is the Biennial World Para Athletics Championships held every two years since 2011.

For more on referring to years, consider reading “What Is the Difference Between Years and Year’s?” and “Is it a Year or An Year? Which Article Is Used Before Year?

Final Thoughts       

To conclude, we can say that both “biennial” and “biannual” are correct when you use them in the right context. While not interchangeable, you use both words in relation to a time frame. 

We use “biannual” for something occurring twice in one year and “biennial” for something occurring every second year.

Since the pronunciation of the two words is very similar, it is imperative to ensure your listener knows which one you are talking about and understands if something is happening biannually or biennially.