ontology

noun

1. philosophyThe branch of metaphysics that addresses the nature or essential characteristics of being and of things that exist; the study of being qua being.

2. philosophyIn 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.

3. philosophyThe theory of a particular philosopher or school of thought concerning the fundamental types of entity in the universe.

4. logicA logical system involving theory of classes, developed by Stanislaw Lesniewski (1886-1939).

5. computer scienceinformation scienceA structure of concepts or entities within a domain, organized by relationships; a system model.

6. (computer science) a rigorous and exhaustive organization of some knowledge domain that is usually hierarchical and contains all the relevant entities and their relations