river vs Arno

river and Arno both are nouns.

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

river (noun)	Arno (noun)
a large natural stream of water (larger than a creek)	a river in central Italy rising in the Apennines and flowing through Florence and Pisa to the Ligurian Sea