Quick answer
Criterion is singular — one criterion. Criteria is plural — several criteria. "The main criteria is cost" is the frequent error; it should be "the main criterion is cost", or "the criteria are". The Greek plural pattern is the same as phenomenon/phenomena.
The core difference
A Greek singular and its plural, one of which is far more often seen.
- criterion — one standard of judgement: a single criterion.
- criteria — more than one: three criteria, the criteria are met.
The pattern
Greek nouns in -on take -a in the plural: phenomenon/phenomena, criterion/criteria. The Latin equivalent runs -um/-a: datum/data, medium/media. Recognising the family means getting all of them right at once.
Which have gone over
Frequently asked questions
Is "one criteria" correct?
No. The singular is criterion. Criteria is plural.
What other words follow this pattern?
Phenomenon and phenomena take the same Greek -on/-a pattern; datum/data and medium/media are the Latin equivalent.
Is criteria as a singular becoming acceptable?
Not yet, unlike data and media. It is still widely treated as an error.
