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

• 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

The findings, published in Neuropsychopharmacology, reveal how caffeine acts on a well-defined brain pathway involved in social memory, the ability to recognize and distinguish people we have encountered before.

From Science Daily • May 30, 2026

The researchers also found that caffeine administered before sleep deprivation restored synaptic communication in the CA2 region and returned plasticity to normal levels.

From Science Daily • May 30, 2026

At the other end, robusta beans, known for their high levels of caffeine, are mass harvested by machines.

From BBC • May 28, 2026

The drink's bright emerald colour has attracted the TikTok generation, and the milder caffeine hit from its green tea powder is suited to health-conscious drinkers who want good sleep.

From BBC • May 28, 2026

Or, what if a regular coffee drinker drives to work in the morning without his usual cup of caffeine?

From "A Deadly Wandering: A Mystery, a Landmark Investigation, and the Astonishing Science of Attention in the Digital Age" by Matt Richtel

Related Words

• cappuccino
• espresso