• synonyms


or caf·fein

[ka-feen, kaf-een, kaf-ee-in]
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noun Chemistry, Pharmacology.
  1. a white, crystalline, bitter alkaloid, C8H10N4O2, usually derived from coffee or tea: used in medicine chiefly as a nervous system stimulant.
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Origin of caffeine

1820–30; < French caféine, equivalent to café coffee + -ine -ine2
Related formscaf·fein·ic [ka-fee-nik, kaf-ee-in-ik] /kæˈfi nɪk, ˌkæf iˈɪn ɪk/, adjectivenon·caf·feine, nounnon·caf·fein·ic, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for caffeine



  1. a white crystalline bitter alkaloid responsible for the stimulant action of tea, coffee, and cocoa: a constituent of many tonics and analgesics. Formula: C 8 H 10 N 4 O 2See also xanthine (def. 2)
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Word Origin

C19: from German Kaffein, from Kaffee coffee
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 caffeine


trimethyl-derivative of xanthine, 1830, from German Kaffein, coined by chemist F.F. Runge (1795-1867), apparently from German Kaffee "coffee" (see coffee) + chemical suffix -ine (2) (German -in). The form of the English word may be via French caféine.

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Online Etymology Dictionary, © 2010 Douglas Harper

caffeine in Medicine


  1. A bitter white alkaloid often derived from tea or coffee and used chiefly as a mild stimulant and in the treatment of certain kinds of headache.
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The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

caffeine in Science


  1. A bitter white alkaloid found in tea leaves, coffee beans, and various other plant parts. It is a mild stimulant. Caffeine is a xanthine and similar in structure to theobromine and theophylline. Chemical formula: C8H10N4O2.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.