what is common between proper noun and common noun?

What is common between a proper noun and a common noun is that both are Words for a person, a place, or a thing.

A proper noun is the name of a specific person, place, or thing.

A common noun is a Word for any general person, place, or thing.

For example:

(proper noun) Abraham Lincoln; (common nouns) a man, a president, a person

(proper noun) The Brooklyn Bridge; (common nouns) a bridge, a landmark, a thing

(proper noun) Coca-Cola; (common nouns) a soda, a beverage, a product, a thing

(proper noun) Denver; (common nouns) a city, a place

(proper noun) 'East of Eden' by John Steinbeck; (common nouns) a story, a title, a thing

(proper noun) SpongeBob SquarePants; (common nouns) a character, a cartoon, a thing

(proper noun) France; (common nouns) a country, a place

(proper noun) Grand Canyon; (common nouns) a canyon, a wonder of nature, a thing, a place