bi-

2 of 4

prefix

1
a
: two
bilateral
b
: coming or occurring every two
bicentennial
c
: into two parts
bisect
2
a
: twice : doubly : on both sides
biconvex
b
: coming or occurring two times
biannual
compare semi-
3
: between, involving, or affecting two (specified) symmetrical parts
bilabial
4
a
: containing one (specified) constituent in double the proportion of the other constituent or in double the ordinary proportion
bicarbonate
b
: di- sense 2
biphenyl
What do bimonthly and biweekly mean?: Usage Guide

Many people are puzzled about bimonthly and biweekly, which are often ambiguous because they are formed from two different senses of bi-: "occurring every two" and "occurring two times." This ambiguity has been in existence for nearly a century and a half and cannot be eliminated by the dictionary. The chief difficulty is that many users of these words assume that others know exactly what they mean, and they do not bother to make their context clear. So if you need bimonthly or biweekly, you should leave some clues in your context to the sense of bi- you mean. And if you need the meaning "twice a," you can substitute semi- for bi-. Biannual and biennial are usually differentiated.

bi-

3 of 4

combining form

variants or bio-
1
: life : living organisms or tissue
bioluminescence
biosphere
2
: biographical
biopic

Bi

4 of 4

symbol

bismuth

Word History

Etymology

Prefix

Middle English, from Latin — more at twi-

Combining form

Greek, from bios mode of life — more at quick entry 1

First Known Use

Noun Or Adjective

1956, in the meaning defined above

Time Traveler
The first known use of bi was in 1956

Dictionary Entries Near bi

Cite this Entry

“Bi.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/bi. Accessed 22 Sep. 2023.

Kids Definition

bi-

combining form
1
: two
bipartisan
2
: coming or occurring every two
bimonthly
3
: into two parts
bisect
Etymology

Combining form

derived from Latin bi- (prefix) "two"

Medical Definition

Bi

symbol
bismuth

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