I remember discussions of flour and butter - different subjects. What if the subject were the same but its two facets are meant: as the amount and variety of data increase(s)..?

  • A grey area; I'd not consider either choice as constituting a problem. – Edwin Ashworth Jul 11 '17 at 15:51

My analysis

The crucial question here is whether the subject is understood as a single thing despite having separately named components or whether the subject is intended as a plural subject.

Consider this sentence:

The give and take of political negotiation has/have become a lost art in recent years.

This is a fairly clear case, because "give and take" is an idiomatic set phrase that English speakers generally interpret as representing a unitary idea. For this reason, you would be very unlikely to hear a fluent English speaker say

The give and the take of political negotiation...

"The give of political negotiation" doesn't express an idiomatically clear notion in modern English parlance, whereas "the give and take of political negotiation" does. And since the subject expresses a unitary idea, we would normally use a singular verb with it:

The give and take of political negotiation has become a lost art in recent years.

In effect, we treat the giving and the taking alluded to in "the give and take of political negotiation" as simultaneous activities, rather than as sequential ones: each party engages in a continuous process of giving and taking in order to reach a mutually acceptable agreement.

Now consider this example:

The bark and bite of the junkyard dog is/are well known.

In this case, we might very well hear a fluent English speaker say

The bark and the bite of the junkyard dog...

And indeed, for physiological reasons, the bark and the bite of a dog are inherently nonsimultaneous events. So it would make a great deal of sense to choose the plural verb in this case:

The bark and bite of the junkyard dog are well known.

Having considered these two contrary but reasonably clear-cut cases, let's look at a slightly expanded version of the OP's example, which Edwin Ashworth in a comment beneath the posted question has very justly described as occupying "a grey area":

The amount and variety of data increase/increases as the pool of source material grows.

Here, the choice between increase and increases as the verb hinges on the speaker's (or writer's) understanding of "the amount and variety." If the speaker conceives of "amount and variety" as a unitary or closely compacted entity that increases as if it were truly a single thing, the speaker has every reason to want to use the singular form of the verb to emphasize that conception:

The amount and variety of data increases as the pool of source material grows.

But if the speaker has in mind two distinct variables that merely happen in this instance to have similar relationships to the growth of the pool of source material, the speaker has every bit as much reason to use the plural form of the verb:

The amount and variety of data increase as the pool of source material grows.

And although it is by no means necessary to do so, the speaker might choose to repeat the definite article before the second noun in order to emphasize the duality of the subject:

The amount and the variety of data increase as the pool of source material grows.

Bryan Garner's guidance

At least at first glance, Bryan Garner, Garner's Modern English, fourth edition (2016) seems to take a somewhat less permissive attitude toward the question than I have, although he clearly acknowledges that compound subjects can take singular verbs in some instances:

SUBJECT-VERB AGREEMENT, A. General Rule. The simple rule is to use a plural verb with a plural subject, a singular verb with a singular subject, But there are complications. If a sentence has two or more singular subjects connected by and, use a plural verb. Yet if the subjects really amount to a single person or thing, use a singular verb {the apple of his eye and the source of his inspiration is Heather}.


D. Compound Subjects Joined Conjunctively. If two or more subjects joined by and are different and separable, they take a plural verb ... [Examples omitted.] But sometimes the two subjects joined by and express a single idea, and hence should take a singular verb {their confusion and uncertainty is understandable}. This is the case with spaghetti and meatballs, which denotes a single dish and therefore takes a singular verb.

The spaghetti and meatballs and inspirational Heather examples call for singular verbs just as indisputable as my give and take example does. But the really interesting example that Garner slips in on his way to spaghetti and meatballs appears at the end of the sentence prior:

Their confusion and uncertainty is understandable.

If you accept the singular verb in that sentence, it seems to me, you are conceding that any tightly bound, difficult-to-disentangle compound subject is fair game for a singular verb. I don't know whether Garner would be willing to view "the amount and variety of data" as sufficiently unified to pass the "confusion and uncertainty" test; but I do know that, by okaying "Their confusion and uncertainty is," he has accepted that the line between acceptable and unacceptable use of singular verbs with compound subjects is a fine and (for the instances close to it) highly subjective one.


Ultimately, from the perspective of rule making, we're stuck with a rather unsatisfactory conclusion: In some instances, a subject of the form "the X and Y" very clearly takes a singular verb; in others, a subject of the form "the X and Y" very clearly takes a plural verb; and in still others, the matter is too close for an outside observer to call, and we must leave it to the speaker to determine which form of the verb more accurately expresses the relationship between the two nouns in the subject.


the verb relates to two descriptors of the same item (data) so the verb is plural since it refers to quantity and variety. Is that clear?

  • Would you consider 'Health and Safety is our prime concern' wrong? – Edwin Ashworth Jul 11 '17 at 15:55
  • @Edwin Ashworth Interesting question. Since "Health and Safety" has effectively becomes a phrase that describes a single function, rather than two distinct and separate functions, I would use "is" in that context... – Kieran H Jul 13 '17 at 9:26
  • And there are many grey areas where some would accept sufficient cohesion to warrant singular agreement in a usage, and others wouldn't. – Edwin Ashworth Jul 13 '17 at 12:25

Amount and variety give a compound subject thus you need the plural verb increase.

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