Does “bimonthly” mean twice per month or every two months? And what about “biweekly” or “biannual”? Do they mean alternating weeks or years, or do they mean twice in the same week or year?
The short answer is “yes.” These “bi–” words go both ways (and that’s a good way to remember it). This can lead to considerable confusion.
One way to reduce the level of confusion is to use “semimonthly” to mean every half month or twice a month, and to use “bimonthly” to mean every other month. Likewise, you can use “semiweekly” to mean twice a week, and “biweekly” or even “fortnightly” to mean every two weeks. Hence, a semiannual sale would happen twice a year, whereas the SPE Digital Energy Conference that alternates between the Amsterdam and Houston locations would be a “biennial” opportunity to the folks not allowed to fly overseas.
The trouble with this solution is that the “bi–” words historically go both ways, so you can’t rely on your audience understanding it your way. To remove confusion completely, you can just say “twice a week/month/year” or “every other week/month/year” and be crystal clear as to what you really mean.
Finally, when you are reading and run across one of these “bi–” words, keep in mind that there are two possible meanings, and if you cannot figure out which one is correct from the context, by all means ask for clarification, especially if you’re about to sign a contract.
Trivia Question of the Day:
Of all the vegetables, only two can live to produce on their own for several growing seasons. All other vegetables must be replanted annually. What are the only two perennial vegetables?
Asparagus and rhubarb.