: 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
His heart hasn’t proved an issue since, with Robinson (who isn’t much of a coffee drinker) chalking it up to taking caffeine shots before matches.
—
The Athletic Uk Staff, The Athletic, 10 Jan. 2025
Avoiding late-night alcohol, caffeine, or large meals Ensuring your bedroom is quiet, cool, and comfortable
Going to bed and getting up at the same times every day
Not using phones, devices, or watching TV in bed
6.
—Mark Gurarie, Verywell Health, 8 Jan. 2025
Starbucks Opens New Store with Views into North Korea
PEOPLE got an early taste of the cortados and were immediately impressed (and buzzing with caffeine).
—Sabrina Weiss, People.com, 2 Jan. 2025
For the journey home, shoppers can still grab a caffeine fix because several coffee chains, including Starbucks, Dunkin' and Caribou Coffee, are open in some locations.
—Gord Magill, Newsweek, 22 Dec. 2024
See all Example Sentences for caffeine 
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The Athletic Uk Staff, The Athletic, 10 Jan. 2025
Avoiding late-night alcohol, caffeine, or large meals Ensuring your bedroom is quiet, cool, and comfortable
Going to bed and getting up at the same times every day
Not using phones, devices, or watching TV in bed
6.
—Mark Gurarie, Verywell Health, 8 Jan. 2025
Starbucks Opens New Store with Views into North Korea
PEOPLE got an early taste of the cortados and were immediately impressed (and buzzing with caffeine).
—Sabrina Weiss, People.com, 2 Jan. 2025
For the journey home, shoppers can still grab a caffeine fix because several coffee chains, including Starbucks, Dunkin' and Caribou Coffee, are open in some locations.
—Gord Magill, Newsweek, 22 Dec. 2024
See all Example Sentences for caffeine
Dictionary Entries Near caffeine
Cite this Entry
“Caffeine.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/caffeine. Accessed 22 Jan. 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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