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

Powered by a blend of squalane, ceramides, peptides, and caffeine, this eye cream expertly improves skin’s moisture levels for plumper, bouncier skin. —Conçetta Ciarlo, Vogue, 8 Oct. 2025

Experts recommend gradually shifting your sleep schedule by 15 minutes each week, avoiding caffeine and screen time close to bedtime, and exercising regularly to manage stress. —Claire Bugos, Verywell Health, 8 Oct. 2025

Each serving delivers omega-3s from algal oil, lutein, zeaxanthin and a gentle 50mg of green tea caffeine for clean, balanced energy. —Adam Mills, MSNBC Newsweek, 8 Oct. 2025

Start your day with a cafécito at Sunrise Cuban Market—the sugar and caffeine rush is sure to wake you up. —Teaghan Skulszki, Travel + Leisure, 7 Oct. 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

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