"A username and password {is / are} required"

Question

I thought that the use of is/are was determined by whether or not the noun was singular or plural. But also, I'm awful at these things.

username is singular. password is singular.

But we are saying a 'username and password' - in my mind, this is two things. Plural, right?

I thought the correct word choice would be 'are'.

However, when I search for both phrases Google returns 82k results when the phrase uses 'are', but 189k when the phrase uses 'is'. That seems to strongly suggest I'm wrong and that it should be 'is'.

Can someone help me understand?

Answer 1

In general, using and makes it plural (though the conjunction or is used with the singular, since only one of the choices is allowed). For example:

Pen and paper are required.

Pen or pencil is acceptable.

So, it should be:

User name and password are required.

That said, even native English speakers make misteaks. oops

Answer 2

It depends entirely on if you are treating them as a single collective or as individual items. Either is possible.

Some people say:

A ^{username and password} is required.

This treats the phrase as a single security measure that's made up of two parts.

If you like, you can assume some missing words from the sentence:

A ^{collective set of security measures consisting of a username and password} is required.

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However, you can also say:

Both ^{a username} and ^{a password} are required.

This treats them as individual things.

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In terms of actual syntax, because of only a single article being used, both of the following are acceptable:

A username and password is required.
A username and password are required.

If you added another indefinite article in front of the second item, then, syntactically, only the plural would work:

✘ A username and a password is required.
✔ A username and a password are required.

Actual syntax aside, there is no strictly right or wrong way of saying it in this case. It's a matter of intention and use.

Answer 3

I would always write "are required" in this context. And this Google Ngram search shows that the are form is far more common in the googel ngram corpus.

In general "X and Y {is/are} Z should use "are" and treat "X and Y" as plural, unless "X and Y" for a celarcut single thing.

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