caffeine

noun

caf·feine ka-ˈfēn

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.

For a caffeine fix paired with handmade confections, indulge in the Dolce Vita Afternoon Tea on weekends. — Condé Nast, Condé Nast Traveler, 13 Oct. 2026 Caffeine Studies show that caffeine can help improve your focus—just in moderation. — Audrey Noble, Vogue, 9 Oct. 2026 Both experts recommended following general sleep hygiene practices, such as maintaining an optimal environment (dark, cool and quiet), keeping a consistent sleep schedule and avoiding sleep-disrupting substances such as alcohol and caffeine. — Melissa Rudy, FOXNews.com, 9 Oct. 2026 Warm yet uplifting with a strong hit of black tea, Still Bloom's cardomom, sesame, and orange top notes hit like a shot of caffeine before dissipating into a mellow, comforting underbelly of musk, rose and cedarwood, to name a few. — ABC News, 9 Oct. 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

See more words from the same year

Cite this Entry

Style

“Caffeine.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/caffeine. Accessed 14 Oct. 2026.

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Kids Definition

caffeine

noun

caf·feine ka-ˈfēn

ˈka-ˌfēn

: a bitter stimulating compound found especially in coffee, tea, cacao, and kola nuts

Medical Definition

caffeine

noun

caf·feine ka-ˈfēn, ˈka-ˌ; ˈkaf-ē-ən

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

caffeinic

ka-ˈfē-nik ˌkaf-ē-ˈin-ik

adjective

caffeine

noun

Examples of caffeine in a Sentence

Word History

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caffeine

noun

Examples of caffeine in a Sentence

Word History

Phrases Containing caffeine

Rhymes for caffeine

Browse Nearby Words

Cite this Entry

Kids Definition

Medical Definition

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