: 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
Avoid caffeine, alcohol, and heavy meals in the evening, which can interfere with falling or staying asleep.
—
Lindsay Curtis, Health, 12 June 2025
Starbucks is testing a new menu item that will give people a protein boost with their morning dose of caffeine.
—Anne Marie D. Lee, CBS News, 11 June 2025
Avoid irritating foods that are spicy, fatty, and/or sugary, as well as dairy, alcohol, and caffeine.
—Cristina Mutchler, Verywell Health, 10 June 2025
Formulated with 96% natural-origin ingredients, this features a blend of niacinamide, caffeine, squalane, peptides, hyaluronic acid, and SPF 25 to reveal hydrated, supple skin.
—Kiana Murden, Vogue, 9 June 2025
See All Example Sentences for caffeine
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Lindsay Curtis, Health, 12 June 2025
Starbucks is testing a new menu item that will give people a protein boost with their morning dose of caffeine.
—Anne Marie D. Lee, CBS News, 11 June 2025
Avoid irritating foods that are spicy, fatty, and/or sugary, as well as dairy, alcohol, and caffeine.
—Cristina Mutchler, Verywell Health, 10 June 2025
Formulated with 96% natural-origin ingredients, this features a blend of niacinamide, caffeine, squalane, peptides, hyaluronic acid, and SPF 25 to reveal hydrated, supple skin.
—Kiana Murden, Vogue, 9 June 2025
See All Example Sentences for caffeine
Cite this Entry
“Caffeine.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/caffeine. Accessed 18 Jun. 2025.
Copy CitationKids 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
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