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

Etymology

Origin of caffeine

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

Compare meaning

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

• theobromine vs. caffeine

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

I had recently told Mona, my older sister, about the caffeine liaison, and I instantly had regretted it as I glanced at her text.

From Los Angeles Times ● Aug. 7, 2026

Coffee and caffeine pills, he said, “do not give me the same mental clarity.”

From The Wall Street Journal ● Aug. 4, 2026

Dr. Rekha Kumar, associate professor of clinical medicine at Weill Cornell Medicine, said most healthy adults can consume up to 400 mg of caffeine a day.

From The Wall Street Journal ● Aug. 4, 2026

Management at the soft-drink giant said Tuesday that a new version of Mr. Pibb, which has 30% more caffeine and extra cherry flavoring, saw more than 20% volume growth in the second quarter.

From MarketWatch ● Jul. 28, 2026

He was like an angry machine, shaking as if he’d just eaten those caffeine pills my mother used to take to stay skinny.

From "Please Ignore Vera Dietz" by A.S. King

Related Words

• cappuccino
• espresso