Is sal a proper common noun?

"Sal" is not a proper common noun. It's a common noun that refers to a general person named "Sal".

Here's the breakdown:

* Proper nouns are specific names of people, places, or things (e.g., John, London, Eiffel Tower). They are capitalized.

* Common nouns are general names for people, places, or things (e.g., person, city, tower). They are not capitalized.

If "Sal" was a specific person's name, it would be a proper noun and capitalized ("Sal"). However, since it's a common noun, it remains lowercase.