What's the "een" in Halloween?
hydrocarbon suffix, from Greek name-forming suffic -ene; it has no real meaning in itself; probably abstracted mid-19c. from methylene (1834). Put in systematic use by Hofmann (1865). "The breakdown of methylene into methyl and -ene, and the identification of the last syllable of methyl with the general suffix -ly, led to the use of meth- as a separate combining-element, as, for example, in methane, methacrylic [Flood].
An unsaturated organic compound, especially one containing a double bond between carbon atoms: ethylene.
A suffix used to form the names of hydrocarbons having one or more double bonds, such as benzene.