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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.

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

In contrast, ants given low or moderate amounts of caffeine quickly became more efficient.

From Science Daily • Apr. 18, 2026

There, they encountered a drop of sugar solution containing 0, 25 ppm, 250 ppm, or 2,000 ppm of caffeine.

From Science Daily • Apr. 18, 2026

By helping ants learn bait locations more quickly and recruit more nestmates, caffeine could increase how effectively poison spreads through a colony before the ants detect it.

From Science Daily • Apr. 18, 2026

Or, what if a regular coffee drinker drives to work in the morning without his usual cup of caffeine?

From "A Deadly Wandering: A Mystery, a Landmark Investigation, and the Astonishing Science of Attention in the Digital Age" by Matt Richtel