Hello everyone, The Merriam-Webster definition of biweekly is: a. Occurring twice a week b. Occurring every two weeks. So if your doctor told you to take the medicine biweekly and meant every two weeks and you interpreted this as twice a week you would have taken twice the quantity as originally intended, thus maybe killing yourself. Yes, this is a silly example. However, this word is so confusing. I believe that it should be discontinued in favor of semiweekly which has only one definition, i.e. occuring twice a week. Thoughts? How did a word ever come to have two conflicting definitions? Thanks so much, drei

I understand it 'every two weeks'. Especially in this kind of cases no one should use terms that can be misunderstood. Note: Please think about this especially if you ever are writing a text that is meant to be translated. Foreign translators have even more possibilities to misunderstand it. I beg this as a translator.

Chambers English Dictionary gives both "every two weeks, or twice weekly", and it is consistent when it comes to bi-yearly which is given as "twice a year, or every two years". I note with interest that they can't decide on which to give precedence to in the order they print the alternatives.

I would also favour the "every two weeks" meaning. I would opt for "twice weekly" to describe something that happens two times in one week.

Living in London I learned the word "fortnight" which means every two weeks or 14 days. I have always thought of bi-weekly as "twice a week".

Here is a pedantic mathematical correction. If your doctor said "take this bi-weekly" meaning every two weeks, and you interpreted it as twice a week, you would actually be taking four times the prescribed dose. OK, sorry, mathematically pedantic moment over. New Fowler's Modern English Usage says that the bi- prefix is the source of endless confusion. It's right (well of course it's right). Don't use this form if you want to communicate unambiguously. It is easy to say twice a week, or once every two weeks. Don't risk death.

you would be taking four times the intended amount of medicine biweekly is usualy only used in situations were one definition would not make sense semiweekly is less commonly known

I had to sign up just to post a reply to this thread because this exact topic has been frustrating me as of late. As it turns out, the term we are looking for is "fortnightly", meaning "Happening or appearing once in or every two weeks". citiation: The Free Dictionary (I'm not allowed to post links to outside sites yet, but I'm sure you could figure it out... thefreedictionary dot com )

An example of the ambiguity of the "bi" words is this: On mortgages, people often pay more than once a month if they want the principal to be reduced quickly (and, therefore, they pay less interest). I have seen many mortgage documents showing "bi-weekly" payments (meaning one payment every two weeks). Unfortunately, I also see many documents stipulating bi-monthly payments which also means one payment every two weeks! I have seen each of these payment terms hundreds of times and have never been able to figure out why these terms mean the exact same thing. As far as I'm concerned, these words should be outlawed! My two cents...

I think there might be even more confusion here. If you pay bi-weekly (fortnightly), you will actually make two more payments in a year than if you pay twice a month (which is semi-monthly or bi-monthly, depending on how you interpret those words.) There are 52 weeks in a year, so a bi-weekly payment schedule gives you 26 payments. There are 12 months, so a semi-monthly payment schedule gives you 24 payments. I'm on a bi-weekly payment schedule on my mortgage, but paying the equivalent of a monthly payment every two payments. This means that I actually make one extra mortgage payment a year, relatively painlessly.

Since it's highly unlikely any doctor would prescribe taking a drug bi-weekly--- in either sense it's too inexact to serve the precise purposes of dosage--- it seems again to come down to a BE/AE difference in actual usage. In BE, where fortnightly is common, bi-weekly becomes 'twice a week.' In AE, where fortnightly is uncommon, bi-weekly takes its place. (Though the OED decries the usage of bi- to mean 'twice in a' as "ambiguous" and "confusing" and recommends using 'semi' instead.)

Clearly your doctor, and everyone else, should avoid saying 'biweekly' and should instead use plain english - twice a week or once every two weeks (for Brits, once a fortnight). 'Bi' in this context clearly confuses the language unnecessarily with an useless import.

That's right - that's how you reduce the principal more quickly than with monthly payments. It also depends on how big your payments are (how many years the mortgage is amortized over). However, bi-weekly and bi-monthly shouldn't mean the same thing but they do! Go figure...

we should totally just toss this word off the face of our lives...especially when talking medicine! we should use twice a week and every two weeks and NEVER use this word again. but I vote for every two weeks, because a bicentennial is 200 years.

Apart from anything else, what kind of practice is it to prepend a latinate bi- to a non-latin stem? Regarding years, I'd always understood biannual as twice a year and biennial (like bicentenennial and millennial) as every two years, but it seems even these can be used interchangeably. For other time periods, twice-weekly, two-weekly, fortnightly, two-monthly are nice and unambiguous

Fortnightly sounds incredibly uppity to my American ears, and I've never heard of "two-weekly" or "two-monthly." In most settings I've come across, "biannual" means every two years, but it's just as ambiguous as biweekly.

Just as a note, since this topic has popped up again, bi-weekly and bi-monthly do not mean the same thing (see above). If I had been paid bi-weekly this year (every other Friday, for example), I would have received 12 checks by the end of May, while if I had been paid bi-monthly (or semi-monthly, see below) I would have received only 10 checks. It can make a great deal of difference when planning a budget. Regarding "bi-weekly", it seems to me that many people and companies use "semi" to indicate halves of something just to avoid the confusion, although "semi-weekly" sounds odd to me. "Semi-annually" and "semi-monthly" do not.

Semiweekly and semimonthly are unambiguous. semiweekly - twice a week semimonthly - twice a month So there's no reason to use bimonthly to mean "twice a month" because there is another word for it. I think bimonthly should be used to mean "every 2 months" and for "every 2 weeks" one can use fortnightly, which is also unambiguous (I am not from the UK).

This might be an old conversation now and I apologize for bringing it up again. When I was a child in Washington and Oregon States, I was taught in school that bi- meant "two of" and di- meant "half-of." This may not be taught there now as I am 42; but it was back then. This made di-weekly 'twice a week', and bi-weekly 'every two weeks'. Until I challenged someone recently on their usage of bi- as "half-of," I still thought this to be a hard-and-fast rule. Imagine my surprise to find that both bi- and di- were ambiguous! I like the semiweekly and fortnightly solution. Thanks, Jamie