Sorry if my subject is a bit long-winded but I didn't know quite how to state it. How about an example?

I'm making suggested edits to an online book that is also shortly coming out in a dead-trees version. Here is the what I pointed out as being erroneous:

parts of memory that is available

I have suggested that are is actually correct, not is. They're insisting that's not the case, that "is" refers to "memory". I'm no expert, but I believe that the necessary form of "to be" needs to correlate with "parts", not memory. The way they've written it just sounds wrong.

EDIT: Sentence in full follows....

Both the stack and the heap are parts of memory that is available to your code to use at runtime, but they are structured in different ways.

  • 1
    Parts of the memory that are available seems correct, to me. Memory is available, true. But only certain parts are available, so the verb is plural.
    – Nigel J
    May 22, 2018 at 1:39
  • 4
    You have to be careful to identify the subject correctly. Parts of the memory that is available is also correct, but means something a little different (but not much). It depends on whether [parts] is modified by [of the memory that is available], meaning parts of the available memory, or whether [parts of the memory] is modified by [that are available], as you seem to parse it. In the first case, the relative clause modifies memory, a singular noun, so is appears. In the second case, it modifies parts of the memory, a plural noun, so are appears. May 22, 2018 at 2:11
  • 1
    What is the sentence in full?
    – BillJ
    May 22, 2018 at 6:14
  • @BillJ Am editing the question to include the full sentence; I was loathe to provide the full sentence at first because I didn't want to muddy the waters with "programmer speak" ;) You will see that it even begins with "Both...." so again, a reference to something plural.
    – Dexygen
    May 22, 2018 at 7:08
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    The sentence does not need that is or that are at all. I will be glad to remove my answer but it really is basic English writing. And I'm surprised no one even said that. This is any editor's pet peeve.
    – Lambie
    Jul 21, 2018 at 19:48

2 Answers 2


At first glance, you would appear to be correct. It makes sense that it should be parts of memory that are available.

The main subject of the sentence is the plural parts, so the verb also takes a plural form.

It's the same principle of construction as:

The three pieces of toast were eaten.
The component parts of the machine were difficult to carry.
The downpour of raindrops that I was protected from by my umbrella didn't last long.

However, they could be correct if the sentence is parsed differently.

Rather than

(parts of memory) that (are available)

it could be interpreted as

(parts of) (memory that is available)

While I would say this is an unlikely interpretation, it's certainly not implausible. (Although, I would add a the in front of memory.)

In order to understand how the sentence should be phrased, you need to understand what's actually being described.

They might also have a semantic issue with memory being divided into components. You can have multiple memories, but a single memory could be considered indivisible. If that's the case (it depends on interpretation), then the phrase "pieces of memory" would need to be rephrased:

The memories that are available.
The memory that is available.

This unstated assumption could then be colouring the verb they want to use.

But then their issue is with the description of the subject, not just with the subject-verb agreement.

  • I would remove the that is altogether.
    – Lambie
    Jul 21, 2018 at 19:48

How to lighten your burden:

Your sentence is:

Both the stack and the heap are parts of memory that is available to your code to use at runtime, but they are structured in different ways.*


Both the stack and the heap are parts of memory available to your code to be used at runtime but they are structured in different ways**.

There is no reason to use a relative pronoun here.

The relative pronoun can be left out when it is not the subject of the clause.

  • 1
    Comments are not for extended discussion; this conversation has been moved to chat.
    – tchrist
    Jul 21, 2018 at 22:10

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