The Greek form eie is the present optative form of eimi (G1510, to be). The optative mood in Greek expresses a wish, possibility, or potential — "might be" or "could be." It is used in indirect questions, wishes, and conditional statements throughout the New Testament.
The optative mood was already declining in the Koine Greek of the NT period, making its appearances notable. The common formula me genoito ("may it not be!") uses the optative to express Paul's vehement denial of a false inference (Romans 3:4, 6; 6:2, 15; 7:7, 13). In Luke 1:38, Mary's "Let it be to me according to your word" uses a related form — expressing humble openness to God's will. The optative of eimi invites theological reflection on potentiality: what might be becomes what is through God's sovereign act.