ethene vs alkene

ethene and alkene both are nouns.

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

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

ethene: 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 ethene include olefin, olefine, gas.

ethene (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