[cri.te.ri.on] n, pl -ria also -ri.ons [Gk kriterion, fr. krinein to judge, decide--more at certain] (1622) 1: a standard on which a judgment or decision may be based
2: a characterizing mark or trait syn see standard usage The plural criteria has been used as a singular for nearly half a century "let me now return to the third criteria --R. M. Nixon" "that really is the criteria --Burt Lance". Many of our examples, like the two foregoing, are taken from speech. But singular criteria is not uncommon in edited prose, and its use both in speech and writing seems to be increasing. Only time will tell whether it will reach the unquestioned acceptability of agenda.