"Abp. A. Keshishian writes, "the Christology of the Armenian Church is fundamentally in line with the Alexandrian Theological School. In fact, the
Cyrillian formula of 'One Nature of the Incarnate Word' consititutes the foundation stone of her Christology. [It should be noted that]first, 'One Nature' is never interpreted in the Armenian Christology as a numerical one, but always a united one. This point is of crucial importance [for the Armenian Church] particularly in its anti-Eutychian and anti-Chalcedonian
aspects. Second the term 'nature' (ousia, in Armenian bnut'iun) is used in Armenian theological literature in three different senses: (a) as essence, an abstract notion, (b) as substance, a concrete reality, (c) as person. In the context of anti-Chalcedonian Christology 'one nature' is used in a sense of 'one person' composed of two natures."
From
http://www.sain.org/Armenian.Church/intro.txt