River Avon vs river

River Avon and river both are nouns.

Word	Noun	Adjective	Verb	Adverb
River Avon	Yes	No	No	No
river	Yes	No	No	No

River Avon (noun)	river (noun)
a river in central England that flows through Stratford-on-Avon and empties into the Severn	a large natural stream of water (larger than a creek)
a river in southwestern England rising in Gloucestershire and flowing through Bristol to empty into the estuary of the Severn