Is Mum a common noun or a proper noun?

Answer 1

Mum is a common noun. Proper nouns are the unique names of people, places, or things. Common nouns are words for general things. Pronouns replace proper and common nouns.

Answer 2

"Mum" is a common noun when used generically to refer to any mother. It becomes a proper noun when used as a specific name or title for someone's mother. For example, saying "my Mum" is using it as a proper noun.