Why that word and not another

Cyril [of Alexandria] chose to speak of this intimate relationship in terms of theosis which, to the Greek mind, was the most intimate relationship one could have with God—more intimate than a synaphic/familiaritas type of union because theosis moves beyond relationship to transformation, a transformation that includes an ontological ascent, although not a change into another nature, although we are “well-nigh” transformed into another nature and provided a union with that nature that does indeed change us.— Theosis, Volume 2, page 176