caffeine
n. uncountablen. a natural substance found in coffee and tea that makes you feel more awake and energetic.
n. a bitter, white crystalline alkaloid that acts as a central nervous system stimulant. Found naturally in the seeds, leaves, and fruit of various plants, it is most commonly consumed in coffee, tea, and soft drinks.
I try not to drink any caffeine after four in the afternoon.
Many people rely on a morning dose of caffeine to help them focus and feel alert during early meetings.
While moderate consumption of caffeine is generally considered safe, excessive intake can lead to jitteriness, increased heart rate, and disrupted sleep patterns in sensitive individuals.
Borrowed from French caféine, from café (“coffee”), or German Caffein, Kaffein (cp. Coffein, Koffein), from Kaffee (“coffee”) (cp. Kaffe, Koffee, Koffe), or Italian caffè (“coffee”) + -ine.
Uncountable when referring to the substance in general; occasionally countable in informal speech when referring to a serving of a caffeinated drink.