Ousia
Ousia is a Greek term meaning being, essence, or substance. In philosophy, it denotes the fundamental nature of a thing—the characteristic that makes a thing what it is, as opposed to its accidents or contingent properties. The word is most closely associated with Aristotle, who treated substances as the primary beings and used ousia to denote the kind of reality that can be predicated of a subject. In his taxonomy, primary substances (individuals) and, more broadly, the kinds or species referred to by secondary substances are organized around a common underlying ousia.
In Christian theology, ousia takes on a technical use related to the nature of God. The term
Across philosophy and theology, ousia thus functions as a foundational term for discussions of what makes something