coeternity

noun

1. (uncountable)Joint eternity; equal eternity with another eternal being

   “1714, Bp George Bull, Some Important Points of Primitive Chriſtianity Maintained and Defended (2nd ed.), volume III, discourse IV: “The Conſubſtantiality and Coeternity of the Son of God with God the Father, Aſſerted; or ſome few Animadverſions on a Treatiſe of Mr. Gilbert Clerke, entituled Anteniceniſmus, ſo far as the ſaid Author pretends to anſwer Dr. George Bull’s Defenſe of the Nicene Faith, &c.”, page 915”