"The commonality and difference among these concepts is/are still unclear. So our paper sheds light on it/them."

‘Is’ or ‘are’ for two uncountable nouns/subjects

According to the above thread, what matters is whether "commonality and difference" is regarded as a compound noun. But I am not sure about this example.

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    I personally wouldn't think of them as uncountable, and would write it with the plural: "The commonalities and differences among these concepts ...." -- This isn't a "split the knot" rewrite, but what would have been the most natural way for me to write it in the first place.
    – R.M.
    Mar 5, 2023 at 14:03
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    The sugar and the flour are in the cupboard. Mar 5, 2023 at 23:38
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    BTW, it should be "between", not "among". Mar 6, 2023 at 3:59
  • @Acccumulation only if "these concepts" are known to number two. The sentence by itself doesn't say how many concepts there are, so "among" is correct. Mar 6, 2023 at 5:09
  • @DawoodibnKareem "Among" is something shared. "Difference" is not shared. It takes "between", regardless of how many things there are. "The difference between nouns, verbs, and adjectives can be subtle" not "The difference among nouns, verbs, and adjective can be subtle". Mar 6, 2023 at 14:03

3 Answers 3


There's something of a US/UK usage split regarding the plurality of nouns. For example, companies, public bodies, and couples / pairs are nearly always singular in AmE, but BrE is often very flexible in this area.

Here's an example matching OP's cited usage which seems okay to me as a Brit, but apparently not everyone would accept it...

Our commonality and difference is sustained by apostolic truth and the promise of the unity of all things in the worship of God

At least with that example, I have no particular objection to using are instead of is. But that's certainly not the case with this example...

In a logical sense, similarity and difference is a binary relation in which similarity excludes difference, and vice versa

...where the entire sentence falls apart if you try to change is to are. I'm just glad that as a Brit I don't have to let things like that bother me!

It may be an inviolable rule1 in AmE that "commonality and difference" must always be syntactically plural in AmE, but that's not true of British English.

No-one could object to The commonalities and differences are unclear, but for the exact version as presented here, I personally prefer the singular verb form. And I very much doubt the writer would accept that he made a "mistake".

1 Obviously even in AmE it's not an inviolable rule. I'm deliberately exaggerating the scope of a "general principle" that I think is slavishly applied far too often in AmE.

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    I've UVd your answer as I think it summarises your point of view well and is a perfectly valid alternative. Mar 5, 2023 at 17:25
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    I think the classic example of "couples/pairs" (at least from my school days) is "salt and pepper." Often used with a singular verb: "Salt and pepper is in aisle 12." Mar 5, 2023 at 17:29
  • @PeterJennings: Now you're putting me on the spot! I toyed with the possibility of upvoting Jay's answer when you commented on it earlier (because initial If we're taking a vote strongly implies opinions differ). But in the end I didn't, because it seemed illogical for me to upvote Jay's answer but downvote yours. And - no disrespect intended - I don't want to remove or reverse my downvote against your answer as it stands, because it's effectively claiming that if I disagree, it must be that I don't know "proper" English! Mar 5, 2023 at 17:49
  • @FumbleFingers That's OK. If you really think my answer is wrong or doesn't contribute anything to the question then DV it. I also UVd Jays answer because, as I said in a previous comment, he has explained it better than I can. Mar 5, 2023 at 21:08
  • @SyntaxJunkie Then there is the exception "Mr and Mrs Smith are going on holiday"", you'd never say "Mr and Mrs Smith is..." Mar 5, 2023 at 21:11

No, "commonality and difference" is not a compound noun, it's a list of two distinct things. Therefore the correct verb is "are". I know it's gibberish, but if it had been "commonality of difference" then it is a compound noun, single item, and would have taken "is"

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    I disagree. It's a stylistic choice (dependent on exact context) whether to treat "commonality and difference" as a singular or plural np. We very rarely use exactly and only those three words as the subject of a verb, but it didn't take me long to find Our commonality and difference is sustained by apostolic truth and the promise of the unity of all things in the worship of God in Google Books. Which so far as I'm concerned is perfectly good English. Mar 4, 2023 at 16:50
  • @FumbleFingers I'm afraid, for once, we must agree to disagree. Jay's answer (below) puts my argument far better than I ever could. Just because something is in print somewhere doesn't make it correct. There are thousands, if not millions of grammatical errors that slip past the proof readers and into print. But as you say, some of it is stylistic not to mention dialect, context or artistic effect. Mar 5, 2023 at 13:36
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    The problem, with such a pedantic approach is that sooner or later you have to confront obviously acceptable usages that don't fit the simplified (and usually, outdated) rules that collectively we call grammar / syntax. Surely you wouldn't argue with In a logical sense, similarity and difference is a binary relation in which similarity excludes difference, and vice versa. To my mind, both that and OP's example work much better as a singular np. Mar 5, 2023 at 16:48
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    This sounds like an example of the perennial argument we have on here, "Is 'correct English' what some authority wrote in a book, or is it discovered by observing what people actually say in real life?" i.e. is it prescriptive or descriptive. I agree that the fact that someone wrote a grammar rule in a book 200 years ago doesn't bind us all for eternity. But on the other hand, if we say that whatever anyone says is by definition "correct English", then there's no point even having a site like this. Personally, I opt for a middle ground: ...
    – Jay
    Mar 6, 2023 at 3:54
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    ... If a rule is well-established and widely recognized, and makes logical sense, and helps us to understand each other better, then I respect it. If a rule doesn't make sense or adds complexity to the language for no apparent reason other than "because somebody wrote it in a book" (like "never use a preposition to end a sentence with"), then I don't respect it.
    – Jay
    Mar 6, 2023 at 3:55

If we're taking a vote, I agree with Peter Jennings! "Commonality and difference" are two things and thus require a plural verb.

Yes, one might say that the phrase "commonality and difference" is two ways of saying the same thing. Difference is presumably the opposite of commonality and vice versa. But grammatically, it's still two different words and two different ideas. If I said, "Freedom and liberty are ...", "freedom" and "liberty" are synonyms but it's still two words and thus should take the plural "are". You wouldn't say "Freedom and liberty is ..." Or "Physical fitness and athletic ability are ..." Etc.

The one caution I would give is that if you are talking about the words themselves, then you might speak of it as one thing. Like, "'Commonality and difference' is the subject of the sentence."

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