river vs River Avon

river and River Avon both are nouns.

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

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