bi-

[bʌɪ]

(also bin- before a vowel)

combining form two; having two: biathlon.

↘occurring twice in every one or once in every two: bicentennial.

↘lasting for two: biennial.

↘Chemistry (in names of compounds) containing two atoms or groups of a specified kind: biphenyl.

↘Chemistry denoting an acid salt: bicarbonate.

Origin

from L., 'doubly, having two'; related to Gk di- 'two'.

Usage

The meaning of bimonthly (and similar words such as biyearly) is ambiguous. Such words can either mean ‘occurring or produced twice a month’ or ‘occurring or produced every two months’. The only way to avoid this ambiguity is to use alternative expressions like every two months and twice a month.