Biannual, Biennial, Semiannual

"Biannual" and "semiannual" both mean "twice a year." "Biennial" means "every two years." Because of the possible confusion between "biannual" and "biennial," use "semiannual" when you want to describe something that occurs twice a year.

So, I'm not sure if the SIDA office really wants us to do this every six months or every two years. According to the memo it would be twice a year, but I doubt that is right...