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See more synonyms for bi on Thesaurus.com
adjective, noun, plural bis, bi's.
  1. Slang. bisexual.
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Origin of bi

by shortening


Symbol, Chemistry.
  1. bismuth.
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  1. plural BI's. built-in.
  2. business intelligence.
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  1. a combining form meaning “twice,” “two,” used in the formation of compound words: bifacial; bifarious.
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Compare bin-.

Origin of bi-1

< Latin, combining form of bis; see twice

Usage note

All words except biennial referring to periods of time and prefixed by bi-1 are potentially ambiguous. Since bi- can be taken to mean either “twice each” or “every two,” a word like biweekly can be understood as “twice each week” or “every two weeks.” To avoid confusion, it is better to use the prefix semi- to mean “twice each” ( semiannual; semimonthly; semiweekly ) or the phrase twice a or twice each ( twice a month; twice a week; twice each year ), and for the other sense to use the phrase every two ( every two months; every two weeks; every two years ).


  1. variant of bio-, especially before a vowel: biopsy.
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Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words


Examples from the Web for bi

Contemporary Examples

Historical Examples

  • Even a well-dressed woman is said to be bi'n gr-ye, that is, she is 'fit to go foreign.'

    All Afloat

    William Wood

  • So ye're sittin' theer, Jecholiah, all bi yersen, doin' nowt but thinkin'!

    The Root of All Evil

    J. S. Fletcher

  • Then, they found health at hum; now, they hunt for it bi travell.

    Josh Billings on Ice

    Henry Wheeler Shaw

  • Bi, not to be confounded with Bey, with which it has only a similar verbal meaning.

  • The Bi is, in the battle, always at the right hand of the Khan.

British Dictionary definitions for bi


adjective, noun
  1. slang short for bisexual (def. 1), bisexual (def. 6)
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the internet domain name for
  1. Burundi
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the chemical symbol for
  1. bismuth
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sometimes before a vowel bin-

combining form
  1. two; having twobifocal
  2. occurring every two; lasting for twobiennial
  3. on both sides, surfaces, directions, etcbilateral
  4. occurring twice duringbiweekly
    1. denoting an organic compound containing two identical cyclic hydrocarbon systemsbiphenyl
    2. (rare in technical usage) indicating an acid salt of a dibasic acidsodium bicarbonate
    3. (not in technical usage) equivalent of di- 1 (def. 2a)
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Word Origin

from Latin, from bis twice


combining form
  1. a variant of bio-
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Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for bi


1956 as a colloquial abbreviation of bisexual.

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word-forming element meaning "two, twice, double, doubly, once every two," etc., from Latin bi- "twice, double," from Old Latin dvi- (cognate with Sanskrit dvi-, Greek di-, Old English twi- "twice, double"), from PIE root *dwo- "two." Nativized from 16c. Occasionally bin- before vowels; this form originated in French, not Latin, and might be partly based on or influenced by Latin bini "twofold" (see binary).

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Online Etymology Dictionary, © 2010 Douglas Harper

bi in Medicine


  1. The symbol for the elementbismuth
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The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

bi in Science


  1. The symbol for bismuth.
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  1. A brittle, pinkish-white, crystalline metallic element that occurs in nature as a free metal and in various ores. Bismuth is the most strongly diamagnetic element and has the highest atomic number of all stable elements. It is used to make low-melting alloys for fire-safety devices. Atomic number 83; atomic weight 208.98; melting point 271.3°C; boiling point 1,560°C; specific gravity 9.747; valence 3, 5. See Periodic Table.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.