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caffeine

American  
[ka-feen, kaf-een, kaf-ee-in] / kæˈfin, ˈkæf in, ˈkæf i ɪn /
Rarely caffein

noun

  1. Chemistry, Pharmacology. a white, crystalline, bitter alkaloid, C 8 H 10 N 4 O 2 , usually derived from coffee or tea: used in medicine chiefly as a nervous system stimulant.

  2. Informal. a drink, usually coffee or tea, containing this stimulant.

    We sipped our caffeine on the balcony with its views of sea stacks, rocky coves, and the ever-changing ocean.
caffeine British  
/ ˈkæfiːn, ˈkæfɪˌiːn /

noun

  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 2 See also xanthine

"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
caffeine Scientific  
/ kă-fēn′ /

  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: C 8 H 10 N 4 O 2 .

Other Word Forms

  • caffeinic adjective
  • noncaffeine noun
  • noncaffeinic adjective

Etymology

Origin of caffeine

First recorded in 1820–30; from French caféine, equivalent to café coffee + -ine -ine 2

Compare meaning

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Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

It was a group powered by caffeine, Johnston said, and their coffee came in handy when they needed a liquid prop to do quick demos with the prototypes to test their absorbency.

From The Wall Street Journal

Coffee and tea contain compounds such as polyphenols and caffeine, which are thought to support brain health.

From Science Daily

“I don’t drink coffee, but I like caffeine. And I like being able to make sure it’s the same amount because I have anxiety disorder and I know how much I can handle.”

From Los Angeles Times

The hitters of lovable Team Italy celebrated home runs with shots of Italian espresso in a dugout dripping with cheek kisses and caffeine.

From Los Angeles Times

These compounds include theobromine and caffeine, which are linked to heart health.

From Science Daily

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.