What's the normal term for a Catholic priest that works in a parish under another one?
In Catholic parishes the priest in charge is commonly known as the pastor. He is normally addresses as Father in everyday conversation. The priests that aid a pastor in the administration of a parish are called either assistant pastors or associate pastors.
Years ago, the term assistant pastor for a priest helping in the administration of a parish was universally the only term used. Nowadays, associate pastor is quite common in certain regions. In everyday conversation, they simply called Father.
Sometimes, assistant pastors are called parochial vicars.
A priest who is residing at a parish and who on occasion helps out in the administration of a parish is known as a priest in residence. These priests are not pastors or assistant pastors because they normally will have some sort of ministry that takes up a large portion of their day. They often are ministering to hospitals or prisons and are called Chaplains.