Homoousian
Homoousian is a term derived from Greek, meaning "of the same substance" or "consubstantial." It became a central concept in the theological debates of the early Christian Church, particularly during the Arian controversy in the 4th century. The primary question at stake was the relationship between God the Father and Jesus Christ.
Arianism, the opposing view, held that Jesus Christ was of a "similar substance" (homoiousian) to the Father,
The Nicene Creed, formulated at the council, explicitly uses the term homoousian to define the relationship