(Greek: hierarchia, sacred rule)
In general, sacred rule or government; hence the totality of sacred ministers in the Church, of distinct and various grades, in which the lower is subordinate to and yields obedience to the higher.
Since one is constituted a member of the hierarchy by ordination, the sacred ministers of the ecclesiastical hierarchy are by Orders and office essentially distinct from the laity.
In the Church we distinguish a twofold hierarchy, one of Orders, the other of jurisdiction.
New Catholic Dictionary