Styx vs river

Styx and river both are nouns.

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

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