Is the word his a common noun or proper noun?

"His" is a possessive pronoun. It's not a noun at all, whether common or proper.

Here's why:

* Nouns name people, places, things, or ideas.

* Pronouns replace nouns to avoid repetition.

* Possessive pronouns show ownership (e.g., his, her, their, ours).

So, while "his" tells us something belongs to someone, it doesn't name the person or thing itself.