ontology

noun

1. (uncountable)The branch of metaphysics that addresses the nature or essential characteristics of being and of things that exist; the study of being qua being.

   “[Martin] Heidegger's concern […] was with ontology, the nature of beings, above all humans. The central question for him was "What is being? What is it for something to be?" He tackled this question not by way of the sciences, but by way of an examination of our prescientific daily life. We are, he argued, not cut off from the world by our mental processes: we are "in the world", in direct contact with our surroundings.”

2. (uncountable)In a subject view, or a world view, the set of conceptual or material things or classes of things that are recognised as existing, or are assumed to exist in context, and their interrelations; in a body of theory, the ontology comprises the domain of discourse, the things that are defined as existing, together with whatever emerges from their mutual implications.

   “Meronym: taxonomy”

   “Research centered on ontology and security argues that the far-right utilizes cultural anxieties to recruit members of dominant cultures within a society who feel left behind in some way.”

3. (countable)The theory of a particular philosopher or school of thought concerning the fundamental types of entity in the universe.

   “The answer to the controversial question of whether Aristotle's ontology includes non-substantial particulars, then, is that it does.”

4. (countable, uncountable)A logical system involving theory of classes, developed by Stanislaw Lesniewski (1886-1939).
5. (countable)A structure of concepts or entities within a domain, organized by relationships; a system model.