While one question could be about what does bi- stand for, my question is what better one word is there for 6 months like daily, weekly, monthly, quarterly.
My guess it there might be one that i.
An annually service sounds wrong because it is wrong;
You're using an adverb where you need an adjective (annual).
The trick is that the adjective form of once a month, monthly, just.
What do lengths of time with the bi prefix mean?
I have understood bicentennial as once every two hundred years, but biannual as meaning twice a year.
Do biweekly and bimonthly mean.