a way of referring to ordination among Roman Catholics, Episcopalians and others: an ordained person is spoken of as "being in holy orders"--meaning that the person has made priestly vows and has been admitted by a bishop into one of the several levels of ordination.
Holy orders, sometimes called sacred orders, is the sacrament conferred on those members of the Catholic community who have been called by God and chosen by the Church for service as deacon, priest or bishop.
Holy Orders in the Roman Catholic, Eastern Orthodox, Oriental Orthodox, Anglican, Assyrian, Old Catholic, and Independent Catholic churches includes three orders: bishop, priest, and deacon. These Churches regard ordination as a sacrament. Other Protestant denominations have varied conceptions of the church offices, but none of them considers ordination a sacrament, and some would not consider their ministries in terms of holy orders at all.