Godhead is a Middle English variant of the word godhood, and denotes the divinity or substance (ousia) of the Christian God, the substantial impersonal being of God, as opposed to the individual persons or hypostases of the Trinity; in other words, the Godhead refers to the "what" of God, and God refers to the "who" of God. The concept is especially important in Christian negative theology, e.g., the theology of the Godhead according to Pseudo-Dionysius. Within some traditions, such as Mormonism, the term is used as a nontrinitarian substitute for the term Trinity, denoting the Father, Son, and Holy Spirit not as a Trinity, but as a unified council of separate beings in full harmony.