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

The lightweight powder refreshes roots with a blend of peptides, biotin, and caffeine. —Conçetta Ciarlo, Vogue, 1 Feb. 2025

Asthma medications and nicotine may amplify caffeine's impact. —Amy Brownstein, Ms, Rdn, Verywell Health, 31 Jan. 2025

This Best of Beauty Award-winning concealer blurs fine lines and texture and doesn't crease throughout the day, thanks to a blend of glycerin and vitamin E—and there's even caffeine to kick puffiness to the curb. —Jennifer Hussein, Allure, 30 Jan. 2025

Limit caffeine to earlier in the day, and don’t drink alcohol within 3 hours of bedtime. —Dominique Fluker, Essence, 24 Jan. 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

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