Biannual commonly means twice a year, but it can also mean every two years. Biennial means every two years or lasting two years. For a schedule readers must act on, write twice a year or every two years.
Two schedules side by side
- “We conduct biannual equipment checks in April and October.” Two checks take place in a single year. Semiannual also means twice a year.
- “The museum hosts a biennial exhibition in even-numbered years.” Two years pass from one exhibition to the next. Biennial can also describe something that lasts two years, such as a biennial plant’s life cycle.
Write out the frequency when it matters
“The board holds biannual reviews” can leave readers guessing. Try “The board reviews the policy twice a year, in January and July” or “The board reviews the policy every two years.” See the Language Portal of Canada’s usage note.
Try it
A conference took place in 2024 and 2026. Its next date is in 2028. Which adjective clearly describes its frequency?
Show the answer
Use biennial. The event happens once every two years.
For more word choices that can change a reader’s interpretation, see the guide to confusing words.
