The word ontology is a compound word, composed of onto-, from the Greek ὤν, on (gen. ὄντος, ontos), i.e. "being; that which is", which is the present participle of the verb εἰμί, eimi, i.e. "to be, I am", and -λογία, -logia, i.e. "science, study, theory".
While the etymology is Greek, the oldest extant record of the word itself is the New Latin form ontologia, which appeared in 1606, in the work Ogdoas Scholastica by Jacob Lorhard (Lorhardus) and in 1613 in the Lexicon philosophicum by Rudolf Göckel (Goclenius); see classical compounds for this type of word formation.
The first occurrence in English of "ontology" as recorded by the OED (Oxford English Dictionary, online edition, 2008) was a work by Gideon Harvey (1636/7-1702): Archelogia philosophica nova; or, New principles of Philosophy. Containing Philosophy in general, Metaphysicks or Ontology, Dynamilogy or a Discourse of Power, Religio Philosophi or Natural Theology, Physicks or Natural philosophy, London, Thomson, 1663. It is likely the word was first used in its Latin form by philosophers based on the Latin roots, which themselves are based on the Greek.
- 1: a branch of metaphysics concerned with the nature and relations of being
- 2: a particular theory about the nature of being or the kinds of things that have existence
Ontology is the philosophical study of the nature of being, becoming, existence, or reality, as well as the basic categories of being and their relations. Traditionally listed as a part of the major branch of philosophy known as metaphysics, ontology deals with questions concerning what entities exist or can be said to exist, and how such entities can be grouped, related within a hierarchy, and subdivided according to similarities and differences.
Ontology, in analytic philosophy, concerns the determination whether some categories of being are fundamental and asks in what sense can the items in those categories be said to "be". It is the inquiry into being in so much as it is being ("being qua being"), or into beings insofar as they exist—and not insofar as (for instance) particular facts can be obtained about them or particular properties belong to them.
Some philosophers, notably of the Platonic school, contend that all nouns (including abstract nouns) refer to existent entities. Other philosophers contend that nouns do not always name entities, but that some provide a kind of shorthand for reference to a collection of either objects or events. In this latter 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. Between these poles of realism and nominalism, stand a variety of other positions; but any ontology must give an account of which words refer to entities, which do not, why, and what categories result. When one applies this process to nouns such as electrons, energy, contract, happiness, space, time, truth, causality, and God, ontology becomes fundamental to many branches of philosophy.