An alternate or older spelling of caffeine, a stimulant alkaloid found in coffee, tea, and other plants that increases alertness and energy.
From German Koffein (1819), derived from Kaffee (coffee) with the chemical suffix -ein. Early chemists used this spelling before caffeine became standardized in English.
Caffein was the original German scientific name—when English chemists borrowed the term, they gradually shifted it to 'caffeine' to match English spelling conventions, showing how international science shapes even our everyday vocabulary.
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