I often have trouble expressing myself when I want to talk about some things (plural) holistically as a single thing.

For example, "differential equations are a form of expression...".

It doesn't seem right to say that somethings (plural) are a something (singular), but I would like to say something like this if it can be done at all correctly.

  • There's no rule in English grammar that disallows different grammatical number on either side of the verb "to be" (which usually should agree with the expression on its left). Consider this Google Ngram for "is/are a form of". Commented Aug 5, 2014 at 20:56
  • rmp251 Yes, you can. Commented Aug 5, 2014 at 20:57
  • "It doesn't seem right" is a very weak reason. This is perfectly grammatical, and perfectly common. And not just in English, but in a great many languages. You will have to clarify why you think it is not acceptable. Failing that, just use it.
    – RegDwigнt
    Commented Aug 5, 2014 at 20:57
  • Could you just refer to them both singularly, as in: "A differential equation is an expression which..." Would that fit your purpose?
    – Liesmith
    Commented Aug 5, 2014 at 20:57
  • Widgets are a type of placeholder.
    – SrJoven
    Commented Aug 5, 2014 at 21:30

1 Answer 1


It is common and acceptable to have a plural noun relating with/to a singular one.

  • Proteolytic enzymes are a special class of hydrolyases called peptidases.
  • The catalytic chemistry of enzymes is the key to designing potent inhibitors and makes them a special class of drug target.
  • Filoviruses are classified as biosafety level 4 by the CDC...
  • Eutherians, also known as placental mammals, are a large portion of the mammalian class.
  • As one might expect, the letters have been an invaluable resource for art historians and biographers.

It is common in formal English, and more so in informal English.

  • The examples are helpful.
    – rmp251
    Commented Aug 6, 2014 at 0:01

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