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

Klinger recommends three or four cups, or roughly 300 to 400 milligrams of caffeine, in order to maximize health benefits while minimizing significant risks. —Embry Roberts, Martha Stewart, 25 Apr. 2026

Four plaintiffs who purchased the Trader Joe's coffee product, sold at the retailer's stores across the country, allege the grocer failed to disclose that the product contained less caffeine than typical coffee products. —Megan Cerullo, CBS News, 24 Apr. 2026

Wendy's Sparkling Energy drinks contain 80-120 mg of caffeine. —Gabe Hauari, USA Today, 23 Apr. 2026

Food is a better source of energy than caffeine, since it can be broken down into glucose (the substance your cells use to produce energy). —Teresa Maalouf, Verywell Health, 23 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