hellhound vs Greek mythology

hellhound and Greek mythology both are nouns.

Word	Noun	Adjective	Verb	Adverb
hellhound	Yes	No	No	No
Greek mythology	Yes	No	No	No

hellhound (noun)	Greek mythology (noun)
a very evil man	the mythology of the ancient Greeks
(Greek mythology) the three-headed dog guarding the entrance to Hades; son of Typhon