Is 'Criteria' Singular or Plural?

Should I write "criteria is" or "criteria are"?

"Criteria" can be singular or plural nowadays, but treating it as singular might irk some of your readers. The safest option is to use "criterion" for the singular and "criteria" for the plural.

More about "Criteria"

The word "criteria" is the Latin plural of "criterion." However, it does not follow that "criteria" is always treated as a plural word in modern English. "Criteria" is sometimes treated as a singular word because its meaning is morphing into a singular version of itself. Here is the most commonly understood meaning of "criteria":

• "The principles or standards against which something is evaluated"
(In this meaning, "criteria" is plural.)

However, not realizing that "criteria" was originally a Latin plural (due to the drop-off of Latin from the national curriculum), people have been using "criteria" as a singular version of itself. In other words, it has now come to mean the following:

• The principle or standard against which something is evaluated.
(In this meaning, "criteria" is singular.)

In this way, "criteria" is following the same path as "agenda" and "data," both of which are routinely treated as singular words in modern English. However, "criteria" is different. As the word "criterion" is still in common use, "criteria" is retaining its plural status far more than "agenda" and "data," whose singular forms have largely disappeared. Nevertheless, it is still common to see "criteria" treated as a singular word in speech and writing.

Here's the dynamic:

• Her criteria is clear. It has to be black.
(This is acceptable, but it might annoy some of your readers. For this reason, we haven't given it a tick.)

The safest option is to use "criterion" when talking about a single standard.

• Her criterion is clear. It has to be black.
  (This is correct, but it also runs a slight risk of sounding pretentious.)

When talking about more than one "criterion," you can only use "criteria." For example:

• Her criteria is clear. It has to be black, and it must be cheap.
(This is wrong because there is more than one criterion.)
• Her criterion is clear. It has to be black, and it must be cheap.
  (This is also wrong because there is more than one criterion.)
• Her criteria are clear. It has to be black, and it must be cheap.
  (This is the only version possible when there is more than one criterion.)

Here is another example:

• Are the criteria available to read? What is the main criterion?