Biannual, Biennial, Bimonthly and Biweekly

I used to get a bit confused when the words biannual and biennial were mentioned. Biannual means twice a year and bienniel means every two years. Thus we go back to our home town biannually, for Chinese New Year and for Christmas. We take a vacation abroad biennially, that is once every two years.

Biennial can also mean lasting for two years. Thus a bienniel plant is a flowering plant that takes two years to complete its lifecycle. It bears leaves, stems and roots in the first year, and then flowers, produces fruits and seeds and dies in the second year.

Now there are confusion where bimonthly (or bi-monthly) is concerned. Bimonthly means occurring every two months, but is often taken to mean twice a month! A similar error is encountered with biweekly (or bi-weekly). I guess to be clear, we should say "twice a month" or "every two months".