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IUPAC Commission of Nomenclature for Heterocyclic Compounds (1957)
Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: Indicating an unsaturated 4-ring heterocyclic compound with nitrogen Full definition →
IUPAC Commission of Nomenclature for Heterocyclic Compounds (1957)
Etymology from Wiktionary, CC BY-SA 4.0.