Is Biannual twice yearly or every 2 years?

[TheFoosa]

I need to write a schedule and I thought that it meant 'occuring twice a year'.

Online sources say it can be used for both.

This is going to make said schedule utterly confusing.

What is the correct definition? TIA

Don't know - interested to see the answers.

In horticulture, if a plant flowers every other year, it is a biennial.

I would use "twice yearly" in your circumstances.

Semi annual for 2 times in a year

I would always read it as twice a year also.

biannual occurs twice in one year
biennial - occurs once every two years

It's confusing! I'd say "twice yearly" for twice a year and "biennial" for every 2 years, but I've no idea if that's actually right!