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From aza- + -iridine. Aza denotes a monocycle with a single nitrogen atom, and -iridine is used to mark a three-membered monocycle.
Etymology from Wiktionary, CC BY-SA 4.0.
aziridine
Today it means: A three-membered heterocycle containing two methylene groups and an imine; the nitrogen equivalent of ethylene oxide. Full definition →