Archpriest
Archpriest is an eccelsiasticlal title for certain priests with supervisory duties over a number of parishes. The term is most often used in Eastern Orthodoxy and Eastern Catholic Churches and may be somewhat analogous to a monsignor in the Catholic Church, but in the Eastern Churches an archpriest wears an additional vestment and, typically, a pectoral cross, and one becomes an archpriest via a liturgical ceremony.
The term may be used in the Latin Rite of the Roman Catholic Church instead of dean or vicar forane.
In the 16th and 17th centuries, during the persecution of Roman Catholics in England, an archpriest appointed from Rome had authority over all of the church's secular clergy in the country. In the present-day Church of England, a rural or area dean resembles an archpriest. In the Latin Rite traditionally a priest's first mass has an archpriest assisting the newly ordained priest, functioning as the deacon otherwise does, but this is only for that event.
Antiquity
In ancient times, the archdeacon was the head of the diaconate of a diocese, as is still the case in the Eastern Orthodox Church, while the archpriest was first the chief of the presbyterium of the diocese. His duties included deputising for the Bishop in spiritual matters when necessary.