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

Ingredients like hyaluronic acid, caffeine, peptides, and brighteners such as licorice root extract and vitamin C help improve skin over time. —Jailynn Taylor, Allure, 13 June 2026

If expectations and conditioning can ease withdrawal from caffeine, similar tools might one day help with dependence on other substances. —Samantha Agate, Kansas City Star, 13 June 2026

Based on a review of multiple studies, there is currently insufficient evidence that everyone needs to cycle caffeine, per Examine. —Samantha Agate, Charlotte Observer, 13 June 2026

There has also been a resurgence in sales of Coca-Cola Zero Zero, which has no sugar or caffeine, said Bloomberg. —Justin Klawans, TheWeek, 12 June 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