: 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
An 16-ounce can of Bang Energy drink contains about 300 mg of caffeine.
—
Gabe Hauari, USA Today, 18 July 2025
The Buzz 50 is the same four ingredients, plus green tea extract for a boost of 50 milligrams of caffeine.
—Fort Worth Star-Telegram, 18 July 2025
Step away from screens, caffeine, and newsfeeds until your nervous system relaxes and curiosity resurfaces.
—Jodie Cook, Forbes.com, 10 July 2025
Consumers who prefer a caramel macchiato from Starbucks for their caffeine hit will likely see a more muted impact on their wallets.
—Amelia Lucas, CNBC, 10 July 2025
See All Example Sentences for caffeine
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Gabe Hauari, USA Today, 18 July 2025
The Buzz 50 is the same four ingredients, plus green tea extract for a boost of 50 milligrams of caffeine.
—Fort Worth Star-Telegram, 18 July 2025
Step away from screens, caffeine, and newsfeeds until your nervous system relaxes and curiosity resurfaces.
—Jodie Cook, Forbes.com, 10 July 2025
Consumers who prefer a caramel macchiato from Starbucks for their caffeine hit will likely see a more muted impact on their wallets.
—Amelia Lucas, CNBC, 10 July 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 29 Jul. 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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