Traditionally listed as a part of the major branch of philosophy known as metaphysics , ontology deals with questions concerning what entities exist or may be said to exist , and how such entities may be grouped , related within a hierarchy , and subdivided according to similarities and differences .
It is part of the major branch of philosophy known as metaphysics . Ontology deals with questions about what things exist or can be said to exist , and how such entities can be grouped according to similarities and differences .