bi-

Bi- is a prefix often associated with timing. It can also be a source of confusion, simply because it can mean both ‘every 2 [periods]’ and ‘twice a [period]'.

The following entries explain the differences between each form. It’s often safer to use a longer phrase so there is no uncertainty over the intended meaning.

Biweekly

Prefer ‘every fortnight’ or ‘twice a week’, depending on your meaning

Bimonthly

Prefer ‘every 2 months’ or ‘twice a month’, depending on your meaning

Biannual

Prefer ‘twice a year’

Biennial

Prefer ‘every 2 years’