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

For a caffeine fix — a necessity at any diner — there are mugs of $1 Cafe du Monde chicory coffee. —Stephanie Breijo, Los Angeles Times, 24 Apr. 2025

Additionally, combining cannabis with other substances, like caffeine, should be approached cautiously due to potential interactions. —Matt Rozo, Mercury News, 23 Apr. 2025

Other foods that are toxic to cats, according to Preventive Vet, include milk and dairy; onions and garlic; alcohol; chocolate; grapes, raisins and currants; caffeine; raw meat; seafood; eggs; raw dough; avocado; and bones. —Thomas G. Moukawsher, MSNBC Newsweek, 17 Apr. 2025

Perhaps the only exception was the coffee shop, where tables were often full by mid-morning as guests awaited their caffeine fix. —David Nikel, Forbes.com, 7 Apr. 2025

Word History

Etymology

German Kaffein, from Kaffee coffee, from French café

First Known Use

circa 1823, in the meaning defined above

Phrases Containing caffeine

• caffeine-free

Rhymes for caffeine

• agin
• alkene
• allene
• ameen
• amin
• amine
• arene
• athene
• baleen
• beeline
• benzene
• between

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