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

While an occasional cola is unlikely to cause harm, regular intake may place strain on the kidneys due to ingredients like phosphoric acid, high-fructose corn syrup, and caffeine. —Md Published, Verywell Health, 2 May 2026

By then, Barnard and his wife had turned vegetarian, cut sugar and caffeine, and watched a sick family member recover on whole foods. —Big Think, 1 May 2026

Coming off an evening that included giddy meetings with Robert De Niro and Andy Serkis, and a morning spent on Good Morning America, Brammall nevertheless appears chipper without the aid of any caffeine during our sit-down. —Savannah Walsh, Vanity Fair, 30 Apr. 2026

Each can contains a lovely 60 mg of caffeine and 30 mg of L-theanine—just enough to add a brighter sheen in the afternoon. —Alaina Chou, Bon Appetit Magazine, 30 Apr. 2026

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