Word Study
ethylidene
CIDE DICTIONARY
ethylidene,
An unsymmetrical, divalent, hydrocarbon radical, C2H4 metameric with ethylene but written thus, CH3.CH= to distinguish it from the symmetrical ethylene, CH2=CH2 . Its compounds are derived from aldehyde. Formerly called also ethidene . [1913 Webster]
For further exploring for "ethylidene" in Webster Dictionary Online