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

Citrus fruits, spicy foods, acidic foods (like tomatoes), chocolate, caffeine, alcohol, and peppermint can all trigger heartburn, so steer clear of those, Bragagnini says. —Sarah Klein, Time, 29 Apr. 2025

Simple changes such as eating smaller meals (with little to no meat) earlier in the evening, cutting back on alcohol and caffeine, and lying in bed reading made the biggest difference for my body when trying to enter a Restorative state and raise my Resilience. —Isabelle Ellingson, Outside Online, 24 Apr. 2025

Poppi Alpine Blast Poppi's new citrus soda with 55 mg of caffeine! —Matt Robison, MSNBC Newsweek, 16 Apr. 2025

In all seriousness, your general health affects your reproductive health, so now’s the time to start taking stock in your eating, drinking, and lifestyle habits, particularly diet, exercise, drug use and caffeine. —Amanda Hess, Vogue, 8 May 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