When Basil and Gregory of Nyssa spoke of 'one ousía, three hypostáseis,' they used 'ousía' in the secondary, abstract sense of essence or universal nature, not as a primary substance
Ousía(as a key concept in metaphysics and theology)
A Greek word meaning 'being' or 'substance'—it refers to what something fundamentally is, the core reality of a thing rather than just how it appears.
Universal nature(as contrasted with individual things)
A characteristic or property that many individual things share, like 'redness' (which applies to apples, fire trucks, and roses) or 'humanity' (which applies to all people).
essence(Medieval realist metaphysics)
The defining nature of a species, held by some to be distinct from and capable of surviving the destruction of all individual members of that species
primary substance(Aristotelian ontology)
The conventional English rendering of Aristotle's 'protê ousia', meaning more literally 'primary being'; the core instance of being upon which all other categories of being depend
Besides monophysitism, Philoponus’ name is associated with the doctrine of tritheism. However, one needs to be aware of an important difference: Whereas monophysitism was a reputable and powerful theological movement in the Eastern church, tritheism was little more than a hostile label given to certain intellectuals who tried to make the mystery of the Trinity intelligible in philosophical language. Philoponus was one such intellectual who, again, resorted to Aristotelian terminology to clarify