Nonwords (and Misused Words) and Words You Should Never Use, Part 6 in a Recurring but Randomly Timed Series

Semi: half of something; e.g., a semicircle is half a circle.

Bi: two of something; e.g., a bicycle has two wheels.

Semimonthly means twice a month; bimonthly means once every two month. The same applies to semi- and biweekly, and most similar constructions, except annual.

Which leads us to one of those super-annoying exceptions of English usage—biannual means twice a year just like semiannual does, rather than once every two years. Why? Probably because the established word for once every two years, biennial, came on the scene about 266 years before biannual did. It also doesn't help that the two words sound very much alike. My advice: don't use either—instead say or write "once every two years" or "twice a year" to avoid confusion.

People always seem to get "semi" and "bi" wrong in the other cases as well. How do you remember which is correct? Semicircle and bicycle—think of those two things and you should be golden.

Cheers.