Po vs river

Po and river both are nouns.

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

Po (noun)	river (noun)
a European river; flows into the Adriatic Sea	a large natural stream of water (larger than a creek)
a radioactive metallic element that is similar to tellurium and bismuth; occurs in uranium ores but can be produced by bombarding bismuth with neutrons in a nuclear reactor