ontology

Ontology is a study of conceptions of reality and the nature of being. In philosophy, ontology (from the Greek , genitive : of being (part. of : to be) and -λογία: science, study, theory) is the study of being or existence and forms the basic subject matter of metaphysics. It seeks to describe or posit the basic categories and relationships of being or existence to define entities and types of entities within its framework.
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(n.)
That department of the science of metaphysics which investigates and explains the nature and essential properties and relations of all beings, as such, or the principles and causes of being.
  

the philosophy of Being, that is, the study of the metaphysical foundations of the universe.
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Noun
1. the metaphysical study of the nature of being and existence
(hypernym) metaphysics