Of course there is no such thing as criterias. Nor are there maximas or minimas. If you had had the opportunity to have Latin in high school you would know that the word form ending in -a designates the plural form, while the -um designates the singular. Criterion being an exception, probably because the language has changed over time from criterum to criterion.
But really, it has not much to do with whether or not you had Latin. Continue reading