Common noun:
* When referring to the general concept of a priest, it is a common noun.
* Example: "The priest gave a sermon on forgiveness."
Proper noun:
* When referring to a specific priest, it becomes a proper noun and should be capitalized.
* Example: "Father John Smith is the priest at our church."
Here's a breakdown:
* Common noun: "priest"
* Proper noun: "Father John Smith"
It's important to consider the context when determining whether "priest" is a common or proper noun.