HETEROUSIANS, composed of ετερος , and ουσια , substance, a sect or branch of Arians, the followers of Aetius, and from him denominated Aetians. They were called Heterousii, because they held, not that the Son of God was of a substance like, or similar to, that of the Father, which was the doctrine of another branch of Arians, thence called Homoousians, Homoousii; but that he was of another substance different from that of the Father.