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

Dine on shrimp tacos or catfish po' boys at Jack’s 128 Pecan or get your caffeine fix at The Girl & The Raven. — Lydia Mansel, Travel + Leisure, 27 June 2026

Per ounce, espresso is packed with more caffeine than drip coffee, thanks to its concentrated nature. — Alexandra Emanuelli, Southern Living, 26 June 2026

The caffeine helps de-puff and brighten the under-eye area almost instantly. — Madeline Merinuk, PEOPLE, 26 June 2026

It’s packed with nourishing ingredients like caffeine to tighten puffy areas and squalane to smooth and plump fine lines and wrinkles. — Kyra Surgent, InStyle, 26 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