>There may also be some confusion here. The three “exact” frequencies that seem operable are as follows

> biannual = twice a year (also known as semi-annual)
> annual = once a year
> biennial = once every two years


Indeed there seems to be an ambiguity that is at least the german english dictionary LEO gives [here](http://dict.leo.org/#/search=biannual&searchLoc=0&resultOrder=basic&multiwordShowSingle=on):

biannual also: bi-annual adj. - semiannual halbjährlich

biannual also: bi-annual adj. - every two years jedes zweite Jahr

biannual also: bi-annual adj. - semiannual zweimal jährlich

This is crazy. I mean with biannual : EVERY TWO YEARS