The Collaborative International Dictionary of English v.0.48:

Criterion \Cri*te"ri*on\ (kr?-t?"r?-?n), n.; pl. Criteria
   (-?), sometimes Criterions (-?nz). [Gr. ????? a means for
   judging, fr. ???? decider, judge, fr. ????? to separate. See
   Certain.]
   A standard of judging; any approved or established rule or
   test, by which facts, principles opinions, and conduct are
   tried in forming a correct judgment respecting them.
   [1913 Webster]

         Of the diseases of the mind there is no criterion.
                                                  --Donne.
   [1913 Webster]

         Inferences founded on such enduring criteria. --Sir G.
                                                  C. Lewis.

   Syn: Standard; measure; rule.
        [1913 Webster]