What is the difference between a brother, a father, a priest and a monk?

In catholic churches, people call a male christian brother, call a priest father. A monk is a brother who live in a monastery.A priest is a ordained monk.
People call a female christian sister, call a nun mother. A nun is a sister who live in a monastery (for sisters).

There are two or three classes of faithful, depending on how you divide them: Clerics, consecrated religious, and lay people. (This may be a oversimplification but for our purposes here it will serve.) Clerics include bishops, presbyters, and deacons. Presbyters are normally called priests, but I used the term "presbyter" since bishops are also priests (but not presbyters). Ok, so a priest is cleric ranking above a deacon, usually below a bishop. A "father" is an affectionate term for a priest. Usually it's an honorific: "Father Smith" or "Father Jim". One would never say "Priest Smith", though one would say "Bishop Smith".
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