What is a formal ontological definition of the nature of God according to the doctrine of the Trinity?

What is a formal [ontological](https://en.wikipedia.org/wiki/Ontology) definition of the nature of God according to the doctrine of the [Trinity](https://en.wikipedia.org/wiki/Trinity) ? Are the Father, the Son and the Holy Spirit ontologically independent entities, each one being particulars of universal divine attributes? If so, wouldn't that mean 3 Gods instead of 1 God? Or should we understand God as one entity comprised of 3 "sub-entities"? But then what would it mean that "the Father is God", "the Son is God", "the Holy Spirit is God"? What does it mean ontologically that "X is God" according to Trinitarianism? Take for example what the Athanasian Creed postulates: *"So likewise the Father is Lord; the Son Lord; and the Holy Ghost Lord. And yet not three Lords; but one Lord"*. Is "Lord" being used here as an entity, as a predicate over entities, or what? ______ In case the question ends up getting closed as off-topic: https://philosophy.stackexchange.com/questions/79273/are-there-any-publications-that-attempt-to-give-a-formal-ontological-definition