At a meeting at work today we discussed having meetings twice a week instead of every other week, and this topic lead to a discussion of "biweekly" verses "semi-monthly," as it always does, which lead to no one knowing which was correct, which is also inevitable. With the magic of wireless networking, I was able to look up an answer, and found this:
"Fowler's Modern English Usage" is unambiguous on this point - the terms are ambiguous, so don't use them if you wish to be understood. It points out that "Rules do not help because they are not universally followed".
Even though biweekly and bimonthly, etc, have primary dictionary definitions meaning "every two weeks" and "every two months" respectively, in common usage they are used roughly equally to mean "twice a week" or "every two weeks", and most dictionaries note both usages. Accordingly, it is best to avoid using the terms altogether - especially in any form of legal contract. If you are having trouble with interpretation while you are drafting the document, why on Earth would you want to leave the term in, for the lawyers to have a field day with later?!
Note that there is one form for which there is a definite distinct usage:
"biannual" = "twice a year" (e.g a biannual plant, if there is such a thing, would flower twice a year.)
"biennial" = "every two years", or "lasting two years" (e.g. a number of cities have biennial arts festivals, every two years.)
However, I would avoid these words as well, because there would be just as much potential for confusion.
It is interesting that there are some "bi-" words for which there is no real likelihood of confusion, even though some of them mean "to double", whereas others mean "to halve":
bilingual = able to speak two languages. (I guess we assume that everyone can speak more than half a language - although this is debatable in some cases. I have a colleague who claims to be bilingual in English and French. Knowing how poor his writing skills are in English, he could be approximately one-quarter literate in two languages, which would make him bilingual, I guess!)
bisect = to cut in half. (But why don't we imagine that we could double an angle, just as easily as halving it?)
bicycle = 2 wheeled vehicle. (Because half a wheel is useless.)
bifurcate = to divide into two branches. (So is this "halving" or "doubling" the original?)
biodegradable = twice as degradable as ordinary plastic (Joke!)
|... Comments made afterwards|