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

Avoid caffeine, alcohol, and heavy meals in the evening, which can interfere with falling or staying asleep. —Lindsay Curtis, Health, 12 June 2025

Starbucks is testing a new menu item that will give people a protein boost with their morning dose of caffeine. —Anne Marie D. Lee, CBS News, 11 June 2025

Avoid irritating foods that are spicy, fatty, and/or sugary, as well as dairy, alcohol, and caffeine. —Cristina Mutchler, Verywell Health, 10 June 2025

Formulated with 96% natural-origin ingredients, this features a blend of niacinamide, caffeine, squalane, peptides, hyaluronic acid, and SPF 25 to reveal hydrated, supple skin. —Kiana Murden, Vogue, 9 June 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