Mississippi vs river

Mississippi and river both are nouns.

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

Mississippi (noun)	river (noun)
a state in the Deep South on the gulf of Mexico; one of the Confederate States during the American Civil War	a large natural stream of water (larger than a creek)
a major North American river and the chief river of the United States; rises in northern Minnesota and flows southward into the Gulf of Mexico