Biannual or biennial?
biannual is an adjective meaning “Occurring twice a year; semiannual”; biennial is an adjective meaning “Happening every two years”. In written English (wordfreq, 2021 data) biennial is about 6.2 times as common as biannual.
What is the difference between biannual and biennial?
| biannual | biennial | |
|---|---|---|
| Part of speech | adjective, noun | adjective, noun |
| Meaning | Occurring twice a year; semiannual proscribedOccurring once every two years; biennial Something occurring twice each year | Happening every two years Lasting for two years A plant that requires two years to complete its life-cycle, germinating and growing in its first year, then producing its flowers and fruit in its second year… |
| Example | none recorded | none recorded |
| Pronunciation | /bʌɪˈanjuːəl/ /baɪˈænjuəl/ | /baɪˈɛn.i.əl/ |
| In writing | about once in every 3 million words | 1.8 times per million words |
Sources: biannual and biennial in the English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0); written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
Every current meaning of biannual and biennial
biannual
- 1
Occurring twice a year; semiannual
- 2
Something occurring twice each year
- 3
proscribedOccurring once every two years; biennial
biennial
- 1
Happening every two years
- 2
A plant that requires two years to complete its life-cycle, germinating and growing in its first year, then producing its flowers and fruit in its second year, after which it usually dies
- 3
Lasting for two years
- 4
An event that happens every two years
Source: the English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0); obsolete, archaic, dialect and rare senses left out.
Which is more common, biannual or biennial?
biannual appears about once in every 3 million words; biennial 1.8 times per million words.
biannual about once in every 3 million wordsbiennial 1.8 times per million words
Source: written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
How many people search biannual vs biennial?
“biannual vs biennial” is searched about 2,400 times a month on Google and 570 on Bing in the United States. Google counts close variants of a query together (“biennial vs biannual”, “biannual or biennial”).
Sources: Google Ads keyword data through DataForSEO and Microsoft Advertising keyword data through DataForSEO, the average month from September 2025 to August 2026.