Commonly Confused Words: Biannual vs. Semiannual vs. Biennial

Imagine your hard work developing your writing skills finally pays off: During a biennial recruitment drive, you landed a full-time job as a content creator who helps writers format short stories. You get a biannual bonus that depends on your semiannual performance review, but there’s just one problem. You’re not exactly sure what biannual, semiannual and biennial mean. Is this a good thing or not?

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There’s a big difference between getting a large check twice a year versus one that you receive once every two years. And how often do semiannual performance reviews happen?

All these terms are great words to describe the frequency at which something happens, but they are only useful if you can use them correctly. Let’s go ahead and clear up biannual vs. semiannual vs. biennial.

Biannual vs. Semiannual vs. Biennial at a Glance

The difference between biannual and semiannual and biennial can be ambiguous, even though each of the three actually has a specific definition. We can break them down into their components for a start:

Annual: Every year
Biannual: Twice a year
Semiannual: Every half year (twice a year)
Biennial: Every two years

You probably already know that annual means “covering the period of a year,” and bi- is the prefix for “two.” Semi- is less obvious, but one definition is “occurring halfway through a specified period of time.”

And then there’s -ennial, a relatively uncommon suffix that means “recurring at or marking intervals of (so many) years.”

The most common word you’ve probably seen is centennial, which means every 100 years, or millennial, which is a tech-savvy thirty-something who is probably running your IT department. Now, let’s put all the pieces together and remove some of the ambiguity.

When To Use Biannual

When we combine bi- (two) and -annual (during a year), we get biannual, or “occurring twice a year.” This is a pretty clear definition, so where does the confusion come from? If a biweekly paycheck comes once every two weeks, then it’s easy to incorrectly apply that logic to biannual and believe that you’ll get your bonus every other year.

Examples of Biannual in a Sentence

Sarah schedules biannual dental check-ups, one in the spring and one in the fall.
The garden club hosts a biannual plant swap, allowing members to exchange rare and unique plants in March and September.
The biannual fashion show in New York City presents new collections in February and August.

When To Use Semiannual

Substituting semi- for bi- gives us semiannual, which for all intents and purposes means the same thing as biannual. However, there is a subtle difference: Since semi- can mean “halfway,” we might infer that semiannual specifically refers to a performance review that occurs every six months on the dot.

Furthermore, it often makes sense to use semiannually vs. biannually because it removes any potential misinterpretation about exactly what biannual means.

Examples of Semiannual in a Sentence

The company holds semiannual performance reviews in January and July.
In June and December, the bookstore offers a semiannual clearance sale.
Claire makes semiannual donations to her local animal shelter every six months.

When To Use Biennial

Finally, we have biennial, probably the least confused of the three. If the company’s centennial celebration happens 100 years after its incorporation, then the biennial recruitment drive occurs once every two years.

Biennial also has alternate yet similar definitions:

Continuing or lasting for two years
A plant that grows vegetatively during the first year and fruits and dies the second

Therefore, your biennial mentorship program will last two years. (We’ll let the landscaper worry about the biennial foxgloves and black-eyed Susans.)

Examples of Biennial in a Sentence

The town hosts a biennial festival that attracts tourists for its vibrant cultural performances and street parades.
The organization publishes a biennial report to inform stakeholders of their progress and goals every two years.
Emily planted biennial flowers in her garden, knowing they would produce lush blooms every other year.

Wrapping Up Biannual vs. Semiannual vs. Biennial

Understanding biannual vs. semiannual vs. biennial tells you that your bonus and performance review will come twice a year, and you won’t have to worry about any new competition until the year after next.

If you want to learn more about properly using similar terms or clearing up other confusing word pairs (like denounce and renounce), the following resources can help guide you through the nuances:

👉 BUY – Commonly Misspelled and Confused Words QuickStudy Laminated Reference Guide
👉 BUY – Merriam-Webster’s Vocabulary Builder
👉 BUY – Grammar Girl’s Quick and Dirty Tips for Better Writing

Can you think of any other subtleties that might dictate when you use biannual or semiannual? Let us know in the comments below, and be sure to explore other confusing words so that you can make sure you’re using them properly.

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Cara Secrist

Cara Linda Secrist is a dedicated Managing Editor with over 15 years of experience in the SEO content industry. Cara’s passion for language and writing was nurtured by her English professor father from a young age, leading her to earn a Bachelor of Arts in French Literature.

Cara developed her writing and editing expertise by working as a teaching assistant at the college Writing Lab and assisting English as a Second Language students to improve their language skills.

Beyond her professional achievements, Cara loves reading, traveling, and directing and acting in local theatrical productions.

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