I wonder if it's correct to say:

"Graphs are a special data structure."

Here, "graphs" are plural, but "a special data structure" is singular. I remember I have seen this type of sentence before, but I cannot give a reference.

  • 3
    Yes, the sentence is correct as it is; So is this one: Bananas are a rich source of potassium; But: Ten miles is a long distance :)
    – user392935
    Aug 13, 2020 at 8:59

1 Answer 1

  • ? Graphs are a special data structure.

It's grammatical, but it doesn't parse very well.

Consider this:

  • ✔ Apples are a joy to eat.

The problem with the particular sentence in the question is that it's unexpected. Even though the syntax is valid, it's not what we'd expect to hear, because on first glance it appears to confuse a plurality with a singularity (although it actually doesn't). As such, it's slightly unidiomatic.

One variation that sounds better simply inserts two words:

  • Graphs are a special kind of data structure.

Other variations replace the verb:

  • Graphs belong to a special data structure.
  • Graphs share a special data structure.
  • Utterly normal mathematical grammar. Hausdorff spaces are a type of topological space. One could use the singular, or not. It's a style matter. Aug 13, 2020 at 13:55

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