from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. Ethical theory concerned with duties and rights.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. The ethical study of duties, obligations, and rights, with an approach focusing on the rightness or wrongness of actions themselves and not on the goodness or badness of the consequences of those actions.

from the GNU version of the Collaborative International Dictionary of English

  • n. The science which relates to duty or moral obligation.

from The Century Dictionary and Cyclopedia

  • n. The science of duty; ethics.


Greek deon, deont-, obligation, necessity (from neuter present participle of dein, to need, lack; see deu-1 in Indo-European roots) + -logy.
(American Heritage® Dictionary of the English Language, Fourth Edition)
From Ancient Greek δέον (deon, "that which is binding, needful, right, proper") + λόγος (logos, "argument"). (Wiktionary)



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  • "I have no idea what is happening in the world beyond my bedroom, but I can write a really good essay on deontology and natural moral law." -Twitter, April 16, 2016

    April 17, 2016

  • JM reckons of all the ontologies that deontology is the one up against it!

    March 24, 2011