Allegheny River vs river

Allegheny River and river both are nouns.

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

Allegheny River (noun)	river (noun)
a river that rises in Pennsylvania and flows north into New York and then back south through Pennsylvania again to join the Monongahela River at Pittsburgh which is the beginning of the Ohio River	a large natural stream of water (larger than a creek)