caf·​feine | \ka-ˈfēn, ˈka-ˌ\

Definition of caffeine 

: 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

Apply waterproof sunscreen throughout the day and drink plenty of fluids (avoid beverages with sweeteners or with caffeine)., "Headed to a Water Park This Summer? Here's What You Need to Know to Stay Safe," 28 June 2018 Rule #3: Lay off the caffeine, and lighten up on alcohol, too. Nina Bahadur, SELF, "I Practiced Perfect Sleep Hygiene for a Week and Here's What Happened," 8 June 2018 And in the morning, give yourself a jolt of energy with the caffeine, vitamin B12, and citicoline in Extra Batteries. Shannon Barbour, The Cut, "5 Vitamin Packs to Boost Your Beauty Routine," 25 May 2018 Also new this year is Mountain Dew Ice, a Dew Lemon Lime soda charged with caffeine. Kathy Flanigan, Milwaukee Journal Sentinel, "Terrapin India Pale Ales added to Summerfest's beer lineup," 17 May 2018 Check out the caffeine-free, 6-ounce golden milk, made with coconut milk, turmeric, ginger, honey and a sprinkling of cinnamon. Alison Bowen,, "Drink This: Golden milk tea at First Sip Cafe," 22 Mar. 2018 These associations were similar for both ground and instant coffee as well and there was no significant difference in risk for people with genetic variants for slower or faster caffeine metabolism. Fiza Pirani, ajc, "Drink a lot of coffee? You’re more likely to live longer, study finds," 4 July 2018 Barn Diva offers up the best brunch in town, and for a morning caffeine jolt, head to Flying Goat, the undisputed Healdsburg coffee shop supreme. Ariel Okin, Vogue, "A Tiny Town Neighboring Napa Is the Next California Culinary Destination," 5 July 2018 The team looked to see who drank coffee, how much and what kind of coffee, and looked for differences in several genes involved in metabolizing caffeine. NBC News, "Coffee is good for you, more science shows," 2 July 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'caffeine.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of caffeine

circa 1823, in the meaning defined above

History and Etymology for caffeine

German Kaffein, from Kaffee coffee, from French café

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Statistics for caffeine

Last Updated

21 Oct 2018

Look-up Popularity

Time Traveler for caffeine

The first known use of caffeine was circa 1823

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English Language Learners Definition of caffeine

: a substance that is found especially in coffee and tea and that makes you feel more awake


caf·​feine | \ka-ˈfēn, ˈka-ˌfēn\

Kids Definition of caffeine

: a substance found especially in coffee and tea that makes a person feel more awake


caf·​feine | \ka-ˈfēn, ˈka-ˌ; ˈkaf-ē-ən \

Medical Definition of caffeine 

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

Other Words from caffeine

caffeinic \ ka-​ˈfē-​nik , ˌkaf-​ē-​ˈin-​ik \ adjective

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Comments on caffeine

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