Question

What is improper noun

Answer 1

improper noun is improper if it were improperly used in a sentence, but I would say or write, “improper usage” rather than “improper noun

Answer 2

improper noun
An improper noun is the name of an object or thing, and is more commonly used than a proper noun.
Eg:
box, card, pen, paper, rifle. ... The correct term is "common" nouns, which means the names of common items, not special, exclusively named items or persons, i.e., table versus King Arthur's Round Table, etc., etc