river vs Styx

river and Styx both are nouns.

Word	Noun	Adjective	Verb	Adverb
river	Yes	No	No	No
Styx	Yes	No	No	No

river (noun)	Styx (noun)
a large natural stream of water (larger than a creek)	(Greek mythology) a river in Hades across which Charon carried dead souls