Is has ruined a noun or pronoun?

"Has" is a helping verb, not a noun or pronoun. It's part of a verb phrase and doesn't stand alone.

For example:

* Has ruined the party. (Helping verb + past participle verb)

* He has ruined the party. (Pronoun + helping verb + past participle verb)

To determine if something is a noun or pronoun, you need to consider its role in the sentence.

* Nouns are words that name people, places, things, or ideas.

* Pronouns are words that replace nouns.

Let me know if you have a specific sentence in mind, and I can help you identify the nouns and pronouns within it!