cri·te·ri·on (kr-tîr-n) KEY
pl. cri·te·ri·a (-tîr-) KEY or cri·te·ri·ons
Greek kritrion, from krits, judge, from krnein, to separate, judge; see krei- in Indo-European roots
cri·teri·al (-l) KEY (Adjective)
Like the analogous etymological plurals agenda and data, criteria is widely used as a singular form. Unlike them, however, it is not yet acceptable in that use.