ethylene vs olefin

ethylene and olefin both are nouns.

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

As nouns, olefin is a hypernym of ethylene; that is, olefin 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
olefin: any unsaturated aliphatic hydrocarbon

Other hypernyms of ethylene include alkene, olefine, gas.

ethylene (noun)	olefin (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