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

---

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

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

Caffeine may also support brain health by reducing inflammation and helping regulate blood sugar metabolism.

From Science Daily • May 13, 2026

"Caffeine is the most widely consumed psychoactive substance in the world, with about 85% of adults in the U.S. using it regularly," said Sabandal, research assistant professor in UTEP's Department of Biological Sciences.

From Science Daily • Mar. 31, 2026

Philip McGovern, whose firm Caffeine & Machine was set up to host official meetings of "petrolheads," believes car lovers unfairly have a reputation.

From BBC • Oct. 7, 2025

Caffeine has a time dilation on it so it could be hours that I’m in there or 30 minutes.

From Los Angeles Times • Aug. 21, 2025

A coffee bar is set off to the side, below a rustic-looking sign that says: Caffeine maintains my sunny personality.

From "The Sea in Winter" by Christine Day

Related Words

• cappuccino
• espresso