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Definitions

caffeine

[ka-feen, kaf-een, kaf-ee-in] / kæˈfin, ˈkæf in, ˈkæf i ɪn /
NOUN
coffee
Synonyms
STRONGEST
cappuccino espresso
STRONG
brew decaf decoction demitasse ink java mocha mud perk
WEAK
battery acid café café au lait café noir forty weight hot stuff jamocha joe varnish remover

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

Only participants consuming caffeine experienced reduced anxiety along with better attention and alertness.

From Science Daily • May 3, 2026

He added: "Coffee is more than just caffeine -- it's a complex dietary factor that interacts with our gut microbes, our metabolism, and even our emotional well-being," said Professor Cryan.

From Science Daily • May 3, 2026

Participants completed psychological assessments, tracked their diet and caffeine intake, and provided stool and urine samples so scientists could analyze changes in gut bacteria and emotional state.

From Science Daily • May 3, 2026

This suggests caffeine improves their ability to learn and remember locations.

From Science Daily • Apr. 18, 2026

I saw Ms. Gruwell waving her arms around like a crazy lady, but no one was reacting to her caffeine high.

From "The Freedom Writers Diary" by The Freedom Writers