There is disagreement as to whether Council of Trent defined seven or eight orders. Chapter II of the decree talks about seven orders, omitting bishops, which would indicate that bishops are merely super-priests and not a separate order. However, chapter IV talks of bishops, distinguishes them from the other ecclesiastical degrees of ministers, and discusses their ordination, indicating that they are a separate order from the presbyteriate. Due to the debate, the ministers in the orders are presented here, without making a claim on three or four orders. A man could be admitted to the major orders only after receiving the minor orders. The vestments common to all those in major orders are the maniple, which was prescribed to be worn at all Masses until the Second Vatican Council. Each order has a distinctive outer vestment for Mass, with the subdeacon wearing the tunicle, the deacon wearing the dalmatic, and priests and bishops wearing the chasuble. Deacons, priests, and bishops also wear the stole, the common garment of Holy Orders.
The reason that these orders were considered "major" was that, with ordination to the subdiaconate, both the recitation of the Liturgy of the Hours and perpetual celibacy became mandatory. Those in minor orders do not have this obligation. Thus, e.g., an acolyte did not have to pray the Divine Office and could marry without Papal dispensation should he leave the seminary. These lesser orders along with the subdiaconate were seen simply as liturgical functions, which could be changed on the authority of the Church. This is exactly what happened in 1972, when Pope Paul VI suppressed the subdiaconate and changed the minor orders to lay ministries. The major and minor orders, including the subdiaconate, however remained in use at conservative Traditionalist Roman Catholic seminaries.