from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun The branch of metaphysics that deals with the nature of being.

from The Century Dictionary.

  • noun The theory of being; that branch of metaphysics which investigates the nature of being and of the essence of things, both substances and accidents.

from the GNU version of the Collaborative International Dictionary of English.

  • noun That department of the science of metaphysics which investigates and explains the nature and essential properties and relations of all beings, as such, or the principles and causes of being.
  • noun (Computers) A systematic arrangement of all of the important categories of objects or concepts which exist in some field of discourse, showing the relations between them. When complete, an ontology is a categorization of all of the concepts in some field of knowledge, including the objects and all of the properties, relations, and functions needed to define the objects and specify their actions. A simplified ontology may contain only a hierarchical classification (a taxonomy) showing the type subsumption relations between concepts in the field of discourse. An ontology may be visualized as an abstract graph with nodes and labeled arcs representing the objects and relations.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun uncountable, philosophy The branch of metaphysics that addresses the nature or essential characteristics of being and of things that exist; the study of being qua being.
  • noun countable, philosophy The theory of a particular philosopher or school of thought concerning the fundamental types of entity in the universe.
  • noun logic A logical system involving theory of classes, developed by Stanislaw Lesniewski (1886-1939).
  • noun computer science, information science A structure of concepts or entities within a domain, organized by relationships; a system model.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun (computer science) a rigorous and exhaustive organization of some knowledge domain that is usually hierarchical and contains all the relevant entities and their relations
  • noun the metaphysical study of the nature of being and existence


from Wiktionary, Creative Commons Attribution/Share-Alike License

Originally Latin ontologia (1606, Ogdoas Scholastica, by Jacob Lorhard (Lorhardus)), from Ancient Greek ὤν ("on"), present participle of εἰμί ("being, existing, essence") + λόγος (logos, "account").


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  • I plus Not-I equals Everything offers a formula for understanding 'being'...if you think about it.

    December 22, 2006

  • The term ontology has its origin in philosophy, where it is the name of a fundamental branch of metaphysics concerned with existence. According to Tom Gruber at Stanford University, the meaning of ontology in the context of computer science, however, is “a description of the concepts and relationships that can exist for an agent or a community of agents.�? He goes on to specify that an ontology is generally written, “as a set of definitions of formal vocabulary.�? - Wikipedia entry for ontology (computer science)

    January 5, 2007