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 enjoy breakfast food a lot, but if I want to have an eventful fun day, I need to just get the breakfast out of the way and get some caffeine in me.

From Los Angeles Times ● Aug. 14, 2026

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

"These include caffeine, capsaicin, menthol and vanillin, not to mention the fact that many of the medicines we use today either come directly from plants or are inspired by plant chemistry."

From Science Daily ● Aug. 3, 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

Lacey says, “Is it that weird feeling you get from so much caffeine that, like, your heart isn’t beating so much as your whole body is beating?”

From "Paper Towns" by John Green

Related Words

• cappuccino
• espresso