Yes and No. Bi-weekly is ambiguous it can mean every two weeks or twice a week so i wouldn't use it because of that confusion.

Hi Niwantha, "Biweekly", as the prefix (bi-) implies, means something that occurs twice per week or once every two weeks. "Fortnightly" means something that occurs once in a fortnight (two weeks). You can also say that something happens twice per month. I hope this helps.

It's a problem in the United States! In the United States, "fortnight" (and "fortnightly") are understood, but not used. "Biweekly" is ambiguous and must be understood from context. It can mean either every two weeks or twice a week. I think it more often means "every two weeks." Certainly, that's what I would expect if someone said "you are paid biweekly" or "The New York Review of Books is published biweekly." The safest thing is to say that the event happens "every other week" or "every two weeks," and people really do say this. For something that happens twice a week the safest thing is to say "twice a week," and it is even better, if possible, to name the days of the week when it happens: "Milk is delivered on Mondays and Thursdays." In theory, "semiweekly" means "twice a week," but almost nobody every uses it. It sounds pedantic. It doesn't clarify the situation because, since it is rarely used, people still need to ask what it means. The same ambiguity exists with "bimonthly" (should mean every two months, often means twice a month).

The regional differences are really interesting here! I didn't know that 'fortnight' is rarely used in the USA. So thanks to everyone for pointing that out. As for 'bi-weekly' I have only ever heard it used to mean two times in one week - and never 'every two weeks'. Likewise I have to say that I have never heard the term "semi-weekly", perhaps it is also regional?

Using such words causes confusion! Now US banks, companies frown on using such terms for it can be liable for a lawsuit! A fornight means two weeks, so fornightly means once every two weeks. Even so, it is better to express explicitly. How many can differentiate the terms, biannually vs biennially without having to pause for awhile? I can't.