The noun 'piece' is a common noun because it is a general word for:
If a noun is not a common noun, it is a proper noun.
A proper noun is the name or title of a specific person, place, or thing.
Examples:
Chat with our AI personalities
yes
The noun 'bench' is a singular, common, concrete noun; a word for a piece of furniture; a word for a thing.
Yes, the noun 'tablet' is a common noun, a general word for a compressed piece of medicine or other substance; a writing pad; a flat piece of stone used for inscription; a small, hand held computer.
Yes, the noun 'stone' is a common noun, a general word for any hardened mass of minerals; a general word for any piece of such a hardened mass.
Yes, the noun 'towel' is a common noun, a general word for any piece of cloth or paper designed for drying or wiping up something.