Homoiousios ( from , "hómoios", "similar" and , "ousía", "essence, being") is a Christian theological term, coined in the 4th century by a distinctive group of Christian theologians who held the belief that God the Son was of a "similar", but not identical, "essence" (or "substance") with God the Father. "Homoiousianism" arose as an attempt to reconcile two opposite teachings, homoousianism and homoianism. Following Trinitarian doctrines of the First Council of Nicaea (325), "homoousians" believed that God the Son was of the same (, "homós", "same") essence with God the Father. On the other hand, "homoians" refused to use the term ("ousía", "essence"), believing that God the Father is "incomparable" and therefore the Son of God can not be described in any sense as "equal" or "same" but only as "like" or "similar" (, "hómoios") to the Father, in some subordinate sense of the term. In order to find a theological solution that would reconcile those opposite teachings, "homoiousians" tried to compromise between the essence-language of "homoousians" and the notion of similarity, held by "homoians". Their attempt failed, and by the First Council of Constantinople (381) homoiousianism was already marginalized.