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

Adraina prefers her caffeine beverages on the sweet side as a latte, while Matt enjoys cold brew and drip. — Katelyn Umholtz, Kansas City Star, 23 July 2026

Aside from its neon yellow-green color, it’s known for it high caffeine content. — Alana Al-Hatlani, Southern Living, 23 July 2026

Previous research has suggested your morning buzz might partly be a placebo—with the ritual of brewing and drinking it doing almost as much heavy lifting as the caffeine itself. — Orianna Rosa Royle, Fortune, 22 July 2026

And because the caffeine content is lower than in coffee, there’s less of a spike-and-crash pattern with mushroom coffee. — Stacey Colino, Time, 22 July 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
• arene
• athene
• baleen
• beeline
• benzene
• between
• bromine

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