If something happens bi-monthly does it happen twice a month or once every two months?

According to my dictionary it can have either meaning, though it is usually used to indicate every two months. Semimonthly is preferred for twice a month.

Thanks Biggles

Although I dont' think I've heard the term semi-monthly

Wouldn't most people refer to something that happens twice a month as being bi-weekly or fortnightly?

I think it would depend on whether the event occurs equal distance apart. If it was on two consecutive days, no. However, if it occurs say every other week, or on specific days like being paid on the 15th and the 30th, I would probably say bi-monthly.

I have just checked my dictionary and that says bi-monthly = appearing every two months.

In that case, then maybe I should be using semi-monthly

I would use 'twice a month', myself, as I find 'semi-monthly' ugly sounding.
Come to think of it , I don't think I use 'bi-monthly' either, but 'every other month'.(K.I.S.S.)!

Well normally, that's the way I'd say it -- twice a month, or once every other month. Or "I get paid on the 15th and 30th!"

My Oxford English Dictionary defines bimonthly as "occuring twice a month or every two months". There is a further note though, which states "bimonthly is often avoided because of the ambiguity of meaning, in favour of two-monthly or twice-monthly or every two months or twice a month". So it seems 'you pays your money and you takes your choice'! Conversely, biannually has no such ambiguity, being defined as "occurring, appearing, etc., twice a year". There is however a related word 'biennial', usually used with reference to plants, which means lasting or occurring every two years.

A related question.

I know that Brits and Aussies use the term 'fortnightly' without a thought, but is it common in other countries like Canada and US?

Just another aside - in France a fortnight is called 'a fifteen days' (une quinzaine/quinze jours). How do they calculate that one?

The only error in counting that way, TT, is that a week which begins on Monday, February 28, should end on Sunday, March 6th, and a fortnight should end on Sunday, March 13th, making 7 or 14 days respectively. However, as you say, their method of counting includes the 'following' day. It still amuses me to hear of two weeks being called 15 days, but that's just the nit-picking mathematician part of me.

Speaking for Canada, I can state that I have never heard anyone not born in Britain, Australia or NZ ever use the word (and they don't use it for long - no one would understand them). We say 'two weeks'.

I just looked up fortnight in my dictionary of etymology, it dates from about 1300. It also mentions the celtic custom of eight day weeks and fifteen day fortnights.

A fortnight in the U.S. occurs only on the BBC channel.