river vs Tombigbee River

river and Tombigbee River both are nouns.

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

river (noun)	Tombigbee River (noun)
a large natural stream of water (larger than a creek)	a river that rises in northeastern Mississippi and flows southward through western Alabama to join the Alabama River and form the Mobile River