Definition of caffeine
: 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 of caffeine from the Web
This scalp treatment contains peptides, proteins, and caffeine.
Some people are metabolically fast at breaking down caffeine, others metabolize it more slowly.
Skip the greasy snacks and sodas with added caffeine, and save some cash by packing your own cooler with no-mess options like lower-sugar drinks and high-protein trail mix to give them some extra energy.
Too much caffeine can interfere with your body’s ability to absorb calcium.
But ecstasy pills laced with other drugs like caffeine or opioids started entering the market, and traffickers began to gravitate more toward selling ecstasy in its powdered form, Chavez said.
Avoiding alcohol use — alcohol and even caffeine can actually dehydrate the body.
But for some people, the caffeine in even moderate amounts of coffee could have a downside.
Even scarier, energy drink manufacturers aren’t even required to disclose how much caffeine is actually in the drink.
These example sentences are selected automatically from various online news sources to reflect current usage of the word 'caffeine.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.
Origin and Etymology of caffeine
German Kaffein, from Kaffee coffee, from French café
First Known Use: circa 1823See Words from the same year
CAFFEINE Defined for English Language Learners
Definition of caffeine for English Language Learners
: a substance that is found especially in coffee and tea and that makes you feel more awake
CAFFEINE Defined for Kids
Definition of caffeine for Students
: a substance found especially in coffee and tea that makes a person feel more awake
Seen and Heard
What made you want to look up caffeine? Please tell us where you read or heard it (including the quote, if possible).