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

These thoughtful beverages, which supplement coffee with mushrooms like reishi, lion’s mane, and chaga, offer a lower dose of caffeine alongside a higher amount of micronutrients. —Deanna Pai, Vogue, 23 Mar. 2025

Instant coffee may be a great choice for folks looking to moderate their caffeine intake or sensitive to caffeine. —Alexandra Emanuelli, Southern Living, 23 Mar. 2025

Fernandez-Mendoza: Good sleep hygiene habits include cutting down on caffeine and alcohol, quitting smoking and exercising regularly. —Julio Fernandez-Mendoza, The Conversation, 20 Mar. 2025

Perhaps your perfect caffeine buzz comes from a cup of something sweet and creamy, paired with a decadent pasty in a pink-walled cafe. —Jenny Berg, Allure, 19 Mar. 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