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 average cup of joe is now less caffeine fix and more wellness ritual. —Brianna Peters, Vogue, 9 Apr. 2026

Echinacea may interact with caffeine and immune-suppressing medications, though more research is needed to confirm this. —Megan Nunn, Verywell Health, 8 Apr. 2026

Drugged and dangerous Scientists found cocaine, caffeine and painkillers in sharks around Eleuthera Island in the Bahamas, according to a study published in the journal Environmental Pollution. —Devika Rao, TheWeek, 7 Apr. 2026

Instead, they are typically now found in supplements, tinctures, teas, powders and functional foods – often combined with other ingredients like caffeine, vitamins or additional herbs. —Daryl Austin, USA Today, 5 Apr. 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
• 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