river vs Tombigbee

river and Tombigbee both are nouns.

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

river (noun)	Tombigbee (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