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

That increased to 24% for those in that age group who had a high amount of caffeine. — Alex Sundby, CBS News, 30 July 2026

Most coffee drinkers can relax about their daily brew, according to a new scientific statement from the American Heart Association on caffeine and heart health. — Gabby Sartori, USA Today, 29 July 2026

While nearly 70% of Americans still consume caffeine daily, many are also seeking its energy-boosting impact with a little more balance. — Clara Ludmir, Forbes.com, 27 July 2026

Many pair the habit with a walk, delay caffeine until after their light session and log it with an app or wearable. — Hanna Wickes, Charlotte Observer, 25 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