Wiktionary
fulvenes
n. (plural of fulvene English)
Wikipedia
Fulvenes
Fulvenes are the class of hydrocarbon obtained by formally cross-conjugating one ring and methylidene through a common exocyclic double bond.
The name is derived from the fulvene. which has one pentagonal ring. Pentafulvene is also called simply fulvene, the parent structure of this class.
Fulvenes are isomer of annulene.