Criteria versus "criterion"?

Question

I came across several forums and articles saying that *criteria* is plural and *criterion* is singular. Some gave me the impression that *criterion* is used to denote a set of rules. What is the correct use of these two words?

Answer 1

Criteria is definitely the plural form of criterion. However, many well-meaning people have confused and misused the two. Criteria has been misused as the singular form so often that it is becoming socially acceptable while use of the word criterion is becoming less popular. If you wish to be grammatically correct, you will remember to use criterion as the singular and criteria as the plural!