Tombigbee River vs river

Tombigbee River and river both are nouns.

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

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