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.

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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

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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 .

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Other Word Forms

• noncaffeine
  noun
• caffeinic
  adjective
• noncaffeinic
  adjective

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Etymology

Origin of caffeine

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

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Compare meaning

How does caffeine compare to similar and commonly confused words? Explore the most common comparisons:

• theobromine vs. caffeine

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Explanation

Good morning! Caffeine keeps you awake! It’s that zippy chemical found in coffee, tea, and sodas. In fact, it comes from the German word for “coffee.” Caffeine is a chemical found naturally in the seeds of some fruits and nuts, like coffee beans and kola nuts. It’s a stimulant, so it makes people feel alert. People love to start their mornings with coffee to help them perk up for the day. The word comes from the German Kaffein, coined in 1830 by a chemist who combined the word for "coffee," Kaffee, with -in, a German chemical suffix.

Example Sentences

See Examples For:

caffeine

If the measurement is higher or lower than “ideal,” the app provides a short blurb about what that could mean, like I could have slept poorly or had too much caffeine.

From Slate ● Oct. 9, 2026

The blood samples also revealed smaller changes associated with fish and caffeine consumption.

From Science Daily ● Sep. 28, 2026

But Tarasenko, 26, is unable to feed his caffeine habit, as his favourite fizzy drink is no longer in stock at his local supermarket.

From Barron's ● Sep. 27, 2026

For instance, an iced coffee might win points at a company in the caffeine business.

From The Wall Street Journal ● Sep. 25, 2026

Judging from his dilated eyes and his maniacal grin, he didn’t need any more caffeine.

From "The House of Hades" by Rick Riordan

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Related Words

• cappuccino
• espresso

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