from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Of, relating to, or concerning duties or obligations: deontic logic.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Pertaining to necessity, duty or obligation, or expressions conveying this.
Greek deon, deont-, obligation, necessity; see deontology.(American Heritage® Dictionary of the English Language, Fourth Edition)
From Ancient Greek δέον ("what is right"); compare deontology (Wiktionary)