The Holy Catholic Church, which is the Mystical Body of Christ, is made up of the faithful who are organically united in the Holy Spirit by the same faith, the same sacraments and the same government and who, combining together into various groups which are held together by a hierarchy, form separate Churches or Rites. Between these there exists an admirable bond of union, such that the variety within the Church in no way harms its unity; rather it manifests it, for it is the mind of the Catholic Church that each individual Church or Rite should retain its traditions whole and entire and likewise that it should adapt its way of life to the different needs of time and place.
These individual Churches, whether of the East or the West, although they differ somewhat among themselves in rite (to use the current phrase), that is, in liturgy, ecclesiastical discipline, and spiritual heritage, are, nevertheless, each as much as the others, entrusted to the pastoral government of the Roman Pontiff, the divinely appointed successor of St. Peter in primacy over the universal Church. They are consequently of equal dignity, so that none of them is superior to the others as regards rite and they enjoy the same rights and are under the same obligations, also in respect of preaching the Gospel to the whole world (cf. Mark 16, 15) under the guidance of the Roman Pontiff.
Vatican II. Orientalium Ecclesiarium. 2-3