The term major orders was a part of the clerical terminology of the Roman Catholic Church before the Second Vatican Council. During the Counter-reformation, the Council of Trent issued a decree outlining seven orders of the clergy. The first four, the minor orders, had various liturgical functions and were conferred upon seminarians studying for the priesthood. The major orders were the final three orders in the list. They are:
The order of sacerdos, which consisted of priests and bishops.
A man could be admitted to the major orders only after receiving the minor orders. The major orders had a common vestment, the maniple, which was worn in liturgical functions until the Second Vatican Council.
The reason why these orders were considered "major" was that both the recitation of the Liturgy of the Hours and perpetual celibacy were requirements for their members. The minor orders did not have this requirement; thus an acolyte did not have to pray the Divine Office and, if he left the seminary before becoming a subdeacon, could still marry. Only the deacon and the sacerdos, though, were a part of the sacrament of Holy Orders, as the rest of the orders were seen as simply liturgical functions which could be changed or removed. This is exactly what happened after the Second Vatican Council when Paul VI in 1972 suppressed the minor orders and the subdiaconate.
Moreover, ecclesiastics, as a general rule, no longer remain in the lower orders, the liturgical functions of which are discharged either by the clergy in the higher orders, as in exorcism, or by the laity, as in singing and serving at the altar.
Minor orders are conferred by the presentation to the candidate of the appropriate instruments, in accordance with the ritual given in the "Statuta Ecclesiae antiqua," a document which originated in Gaul about the year 500.
The usual minister of these orders as of the others, is a bishop; but regular abbots who have received episcopal benediction may give the tonsure and minor orders to their subjects in religion.
The conferring of the Sacrament of Holy Orders (diaconate and priesthood) and the conferring of tonsure, the minor orders (porter, lector, exorcist, and acolyte) and the subdiaconate.
Required ages for majororders are 21 for the subdiaconate, 22 for the diaconate, and 24 for the priesthood.
The orders are the episcopate, the priesthood and the diaconate.