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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.

The Crown star Claire Foy has said she had parasites for five years after catching an infection, and no longer drinks caffeine as a result.

From BBC

People have relied on these same compounds for generations, using them in pain relief, medical treatments, and everyday products including caffeine and nicotine.

From Science Daily

Something broke in my body when I turned 32 and my caffeine tolerance plummeted seemingly overnight.

From Salon

I recently stopped drinking caffeine, but I couldn’t kick the ritual, so I have a decaf latte every single morning I make at home with my little Nespresso pods.

From The Wall Street Journal

This is my 20-minute meditation with a little caffeine and the sun on my skin.

From Los Angeles Times

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.