River Lethe vs Greek mythology

River Lethe and Greek mythology both are nouns.

Word	Noun	Adjective	Verb	Adverb
River Lethe	Yes	No	No	No
Greek mythology	Yes	No	No	No

River Lethe (noun)	Greek mythology (noun)
(Greek mythology) a river in Hades; the souls of the dead had to drink from it, which made them forget all they had done and suffered when they were alive	the mythology of the ancient Greeks