Make Your Editor Cry: Biennial vs. Biannual (& Biweekly, Bimonthly)

Make Your Editor Cry:  Biennial vs. Biannual (& Biweekly, Bimonthly)

This can be ambiguous because these words are each formed from two different senses of the prefix “bi” meaning either “occurring every two” or “occurring two times.”

Biennial” (there is no hyphen) means once every two years, so the “bi” in this word means “occurring every two.” Biennials are plants that live two years, like carrots and sugar beets, that bear flowers and fruit only in the second year. If you hire a chimney sweep to perform biennial cleaning of your stovepipes, he will come out once this year and again two years hence. Biennial conventions, celebrations, competitions, and sports events come every two years. With the Olympics, the Summer Games and Winter Games alternate on a biennial basis.

Biannual” (still no hyphen) means twice a year, so the “bi” in this word means “occurring two times.” It basically means the same thing as semiannual (and still no hyphen). Therefore, if you hire a chimney sweep to perform biannual cleaning of your stovepipes, he will come out once in the summer and once in the winter of the same year.

Examples:

Regular meetings of the legislature are biennial during odd-numbered years, although special sessions may be called by the governor.
Many insurance plans will cover things like root canals and emergency surgery, but will forego paying for biannual checkups.

Funny anecdote. Webster gets the entry for biennial exactly right. Kudos!

Uh, oh. Whoopsie! Webster gets the entry for biannual dead wrong.

According to Webster, biennial means occurring every two years, but biannual can mean either occurring twice within a year (which is correct) or every two years (which is dead wrong). Listen to Webster on this point and you might end up in a bit of a jam. If you say “biannual” when you mean “biennial,” you’ll probably double the number of times something takes place in a single year and quadruple it over a 2-year period.

While Webster concedes that biennial strictly means occurring every two years, I believe someone on their staff conflated the word biannual with words like bimonthly and biweekly. Technically, a biweekly meeting occurs every two weeks and a semiweekly one occurs twice a week, but very few people ever get this straight.

Speaking of bimonthly and biweekly, in terms of usage the “bi” in these words can actually mean either “occurring every two” or “occurring two times.” So that’s ambiguous and confusing. For clarity, consider using twice-weekly or semi-weekly (Hey! Hyphens!) instead. Or couch bimonthly or biweekly in careful if somewhat on-the-nose context like “the next bimonthly meeting is scheduled for April 14th.”

Examples:

Feeding America organized a biweekly grocery and laundry service.
The biweekly mortgage loan was started in Canada and is now offered by lenders in the United States.
Undercover officers recorded video of some of the bimonthly dog fights held at eight separate secluded sites in the county.
The IRS explained that $2,725 spread across 24 bimonthly paychecks equals about $113 in additional income per pay stub, which may not sound as enticing as a bigger lump sum.

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