What year is it?

Add comment January 24th, 2009

When something occurs every year, it’s called “annual.”

For something that occurs twice a year, we have two terms, which seems appropriate on some level: “biannual” and “semiannual.”

Most other such words use “-ennial” for the “year” part.

“Biennial” is every other year. To distinguish it from “biannual,” it helps to think of it as “once every two years” to match other members of the family: “quadrennial,” once every four years (as in U.S. presidential elections); “centennial,” once in 100 years; “sesquicentennial,” 150 years; and “bicentennial,” 200 years.

Slightly straying from this parade of logic, an annual plant is one that lasts only one year (or season). A plant that makes an annual comeback is a “perennial.”