Look-alike words

Biannual vs. Biennial

Biannual means twice a year. Biennial means once every two years. A biannual sale happens in spring and fall; a biennial art show happens in 2026, 2028 and so on. Semiannual is a clearer word for twice a year.

Word	Part of speech	Meaning
biannual	adjective	happening twice a year, often about six months apart
biennial	adjective	happening once every two years
biennial	noun	a plant that lives for two years and flowers in the second; also an event held every two years

Biannual

adjective: happening twice a year, often about six months apart

Our dentist sends biannual reminders for checkups.
The club holds a biannual meeting in March and September.

Biennial

adjective: happening once every two years

The city hosts a biennial jazz festival in odd-numbered years.
The board reviews its rules on a biennial schedule.

noun: a plant that lives for two years and flowers in the second; also an event held every two years

Parsley is a biennial, so it flowers in its second summer.
The art biennial draws visitors from around the world.

How to remember the difference

Biannual keeps the whole word annual inside it, so it happens within one year: twice. Biennial, like a biennial plant, takes two full years.

Good to know

Because the two words are so easy to mix up, and some dictionaries even list every two years as a second meaning of biannual, careful writers often use semiannual for twice a year and every two years instead of biennial.

Spot the mistake

The festival is ~~biannual,~~ biennial, so the next one is two years from now.
Correct: The festival is biennial, so the next one is two years from now.
We change the smoke alarm batteries on a ~~biennial~~ biannual schedule, in spring and fall.
Correct: We change the smoke alarm batteries on a biannual schedule, in spring and fall.

Check yourself

Pick the word that fits each sentence.

1. The sale happens every January and July.

2. The conference was held in 2024 and will return in 2026.