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 docuseries also included an allegation that Michaels was aware of the administration of caffeine pills to contestants — claims that Michaels quickly and vigorously denied. —Ryan Coleman, Entertainment Weekly, 14 Oct. 2025

Both the caffeine and coconut water in this drink offer potential benefits to your health and mental function. —Mark Gurarie, Verywell Health, 14 Oct. 2025

There’s hydrating hyaluronic acid, caffeine for puffiness, soothing aloe leaf, and green tea for antioxidant protection. —Marie Lodi, StyleCaster, 13 Oct. 2025

The store also sells packaged drinks that combine THC and caffeine, which allows users to experience a high without the sleepy effect. —Sara Hansen, Denver Post, 13 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