The Works of Dionysius the Areopagite, tr. by John Parker, [1897], at sacred-texts.com
For what reason all the Heavenly Beings are called, in common, Angels.
This, then, in our judgment, is the reason for the appellation Angelic in the Oracles. We must now, I suppose, enquire for what reason the theologians call all the Heavenly Beings together "Angels;" but when they come to a more accurate p. 22 description of the supermundane orders, they name exclusively, "angelic rank," that which completes the full tale of the Divine and Heavenly Hosts. Before this, however, they range pre-eminently, the Orders of Archangels, and the Principalities, the Authorities, and Powers, and as many Beings as the revealing traditions of the Oracles recognize as superior to them. Now, we affirm that throughout every sacred ordinance the superior ranks possess the illuminations and powers of their subordinates, but the lowest have not the same powers as those who are above them. The theologians also call the most holy ranks of the highest Beings "Angels," for they "also make known the supremely Divine illumination. But there is no reason to call the lowest rank of the celestial Minds, Principalities, or Thrones, or Seraphim. For it does not possess the highest powers, but, as it conducts our inspired Hierarchs to the splendours of the Godhead known to it; so also, the saintly powers of the Beings above it are conductors, towards the Divine Being, of that Order which completes the Angelic Hierarchies. Except perhaps some one might say this also, that all the angelic appellations are common, as regards the subordinate and superior communication of all the celestial powers towards the Divine likeness, and the gift of light from God. But, in order that the question may be better investigated, let us reverently examine the saintly characteristics set forth respecting each celestial Order in the Oracles. p. 23