The American Heritage® Dictionary of the English Language: Fourth Edition. 2000.
bi–1
VARIANT FORMS:
or bin–
PREFIX:
1a. Two: biform.b. Both: binaural.c. Both sides, parts, or directions: biconcave.2a. Occurring at intervals of two: bicentennial.b.Usage Problem Occurring twice during: biweekly.3a. Containing twice the proportion of a specified chemical element or group necessary for stability: bicarbonate.b. Containing two chemical atoms, radicals, or groups: biphenyl.
ETYMOLOGY:
Latin bis, bi-, twice, and bn, two by two; see dwo- in Appendix I.
USAGE NOTE:
Bimonthly and biweekly mean “once every two months” and “once every two weeks.” For “twice a month” and “twice a week,” the words semimonthly and semiweekly should be used. Since there is a great deal of confusion over the distinction, a writer is well advised to substitute expressions like every two months or twice a month where possible. However, each noun form has only one sense in the publishing world. Thus, a bimonthly is published every two months, and a biweekly every two weeks.
n
