study of the nature of being, becoming, existence or reality, as well as the basic categories of being and their relations (philosophy)

Ontology is the philosophical study of the nature of being, becoming, existence, or reality. It is part of the major branch of philosophy known as metaphysics.

Parmenides was among the first to propose an ontological characterization of the fundamental nature of reality

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.



The word ontology ('study of being') comes from

onto- (Greek: ὄν, on;[note 1] GEN. ὄντος, ontos, 'being' or 'that which is') and
-logia (-λογία, 'logical discourse').[1][2]



Ontology asks whether "categories of being" are fundamental.

Some philosophers, of the Platonic school, say that all nouns (including abstract nouns) refer to actual entities. Other philosophers contend that nouns do not always name entities. They think some are a kind of shorthand for a collection of either objects or events.

In this view, mind, instead of referring to an entity, refers to a collection of mental events experienced by a person. Society refers to a collection of persons with some shared characteristics, and geometry refers to a collection of a specific kind of intellectual activity.[3]

Between these poles, called realism and nominalism, are other positions. Any ontology must give an account of which words refer to entities, which do not, why, and what categories result.

  1. ὄν is the present-tense participle of the verb εἰμί (eimí, 'to be' or 'I am').


  1. "ontology". Online Etymology Dictionary.
  2. εἰμί. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at Perseus Project.
  3. Griswold, Charles L. (2001). Platonic writings/Platonic readings. Penn State Press. p. 237. ISBN 9780271021379.