Within Christianity, especially in Eastern Christianity and Roman Catholicism, the term cleric refers to any individual who has received the clerical tonsure, including deacons, priests, and bishops. In Roman Catholicism, the tonsure was a prerequisite for receiving any of the minor orders or major orders before the minor orders and the subdiaconate were abolished following the Second Vatican Council. Thus those individuals who have received the tonsure, but are not deacons, priests, or bishops, are properly referred to as clerics. Minor Orders are still given in the Eastern Catholic Churches, and 'cleric' is the normal title given to seminarians and those with minor orders.
The term "clerk" derives from "cleric," since in medieval times the clergy were one of the few groups who could read, and therefore were often employed to do bookkeeping and similar work. The term "clerical work" continues to this day to refer to such functions.