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

Key Takeaways Green tea contains caffeine and antioxidants, which may support metabolism, appetite management, and the fat-burning process in the body. —Cristina Mutchler, Verywell Health, 16 Dec. 2025

Just steer clear of alcohol and caffeine, both of which can disrupt your rest. —Alesandra Dubin, Southern Living, 15 Dec. 2025

For the caffeine dependent, this popular french press gained the stamp of approval from more than 6,000 shoppers in the past month, and this wooden cooking spoons set—purchased 10,000 times in the past month—adds an authentic feel to the kitchen. —Stephanie Osmanski, Better Homes & Gardens, 12 Dec. 2025

His caffeine consumption had not been recorded upon admission to the hospital. —Angelica Stabile, FOXNews.com, 12 Dec. 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