caffeine

noun

caf·​feine ka-ˈfēn How to pronounce caffeine (audio)
ˈka-ˌfēn
: a bitter alkaloid C8H10N4O2 found especially in coffee, tea, cacao, and kola nuts and used medicinally as a stimulant and diuretic

Examples of caffeine in a Sentence

Her doctor told her to avoid caffeine.
Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Twenty-eight of the sharks had detectable levels of caffeine, two common over-the-counter anti-inflammatory painkillers, or, in one instance, cocaine in their blood, according to the study. Kerry Breen, CBS News, 26 Mar. 2026 Tronque’s formula harnesses green coffee and caffeine to help support skin elasticity, while Cyklar’s blend leans into barrier care with ceramides, urea, and squalane. Conçetta Ciarlo, Vogue, 23 Mar. 2026 While true teas generally have less caffeine than coffee, the tannins alone can still interfere with nutrient absorption. Lauren Manaker, SELF, 23 Mar. 2026 And don’t consume any alcohol or caffeine. Jasmine Mendez follow, Los Angeles Times, 23 Mar. 2026 See All Example Sentences for caffeine

Word History

Etymology

German Kaffein, from Kaffee coffee, from French café

First Known Use

circa 1823, in the meaning defined above

Time Traveler
The first known use of caffeine was circa 1823

Browse Nearby Words

Cite this Entry

“Caffeine.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/caffeine. Accessed 29 Mar. 2026.

Kids Definition

caffeine

noun
caf·​feine ka-ˈfēn How to pronounce caffeine (audio)
ˈka-ˌfēn
: a bitter stimulating compound found especially in coffee, tea, cacao, and kola nuts

Medical Definition

caffeine

noun
: a bitter alkaloid C8H10N4O2 found especially in coffee, tea, and kola nuts and used medicinally as a stimulant and diuretic
caffeinic adjective

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