ethylene vs alkene

ethylene and alkene both are nouns.

Word	Noun	Adjective	Verb	Adverb
ethylene	Yes	No	No	No
alkene	Yes	No	No	No

As nouns, alkene is a hypernym of ethylene; that is, alkene is a word with a broader meaning than ethylene:

ethylene: a flammable colorless gaseous alkene; obtained from petroleum and natural gas and used in manufacturing many other chemicals; sometimes used as an anesthetic
alkene: any unsaturated aliphatic hydrocarbon

Other hypernyms of ethylene include olefin, olefine, gas.

ethylene (noun)	alkene (noun)
a flammable colorless gaseous alkene; obtained from petroleum and natural gas and used in manufacturing many other chemicals; sometimes used as an anesthetic	any unsaturated aliphatic hydrocarbon