Definition of bi- in English:

bi-

combining form

  • 1Two; having two.

    ‘bicoloured’
    See also bin-
    ‘biathlon’
    1. 1.1 Occurring twice in every one or once in every two.
      ‘bicentennial’
    2. 1.2 Lasting for two.
      ‘biennial’
    3. 1.3 Doubly; in two ways.
      ‘biconcave’
    4. 1.4Chemistry (in names of compounds) containing two atoms or groups of a specified kind.
      ‘biphenyl’
    5. 1.5Chemistry Denoting an acid salt.
      ‘bicarbonate’
    6. 1.6Zoology Botany (of division and subdivision) twice over.
      ‘bipinnate’

Usage

The meaning of bimonthly (and other similar words such as biweekly and 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. Biannual and biennial are also confusing: biannual means ‘occurring twice a year’ and biennial means ‘occurring every two years’

Origin

From Latin, ‘doubly, having two’; related to Greek di- ‘two’.

Pronunciation

bi-

/bʌɪ/