bi-
- having two: biangular, bicapsular
- doubly, on both sides, in two ways or directions: biconvex, bilingual
- coming, happening, or issued every two (specified periods): biennial, biweekly
- coming, happening, or issued twice during every (specified period): often replaced by semi- or half-, to avoid confusion with preceding sense: bimonthly, biyearly
- using two or both: bilabial, bimanual
- joining two, combining or involving two: bilateral, bipartisan
- Bot., Zool. twice, doubly, in pairs: bifurcate, bipinnate
- Chem.: usually replaced by di- (sense ) except in the names of acid salts [potassium bitartrate]
- having twice as many atoms or chemical equivalents for a definite weight of the other constituent of the compound: sodium bicarbonate
- in organic compounds, having a combination of two radicals of the same composition: biphenyl
See bi- in American Heritage Dictionary 4
or bin-
prefixa. Two: biform.
b. Both: binaural.
c. Both sides, parts, or directions: biconcave.
a. Occurring at intervals of two: bicentennial.
b. Usage Problem Occurring twice during: biweekly.
a. Containing twice the proportion of a specified chemical element or group necessary for stability: bicarbonate.
b. Containing two chemical atoms, radicals, or groups: biphenyl.
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.
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