Is a proper noun?

"A" is not a proper noun. It is an indefinite article, used to indicate that the noun it precedes is not a specific person, place, or thing.

Proper nouns are always capitalized and refer to specific people, places, or things.

For example:

* Proper noun: John, Paris, Amazon River

* Common noun: man, city, river

Let me know if you have any other questions!