Rio Bravo vs river

Rio Bravo and river both are nouns.

Word	Noun	Adjective	Verb	Adverb
Rio Bravo	Yes	No	No	No
river	Yes	No	No	No

Rio Bravo (noun)	river (noun)
a North American river; boundary between the United States and Mexico; flows into Gulf of Mexico	a large natural stream of water (larger than a creek)