I came across this sentence online:

C extensions are a big part of the Ruby ecosystem.

Now, the word "C extensions" is the subject of the sentence and it's in plural form. The writer wants to say that the ability to write extensions in C (a popular programming language!) is a major part of programming practices inside Ruby (another programming language) environment. With this meaning in mind, is it correct to use the plural auxiliary 'are' to refer to a subject, although in plural form, functions as one unit or as a whole?!

If I were to write the same sentence, I would probably say:

C extensions is a big part of the Ruby ecosystem.


  • 1
    Plural is plural. Extensions are extensions.
    – RegDwigнt
    Oct 28, 2014 at 10:52
  • Does that mean whenever I find a word in plural, it must come with 'are' no matter what?
    – 7kemZmani
    Oct 28, 2014 at 10:54
  • @Abdul, if you wanted to use is, you could recast the sentence as "Writing C extensions is...". But as it is currently worded, Reg++ is right; you must use are.
    – Dan Bron
    Oct 28, 2014 at 10:57
  • @Abdul: That is a somewhat wishy-washy way of putting it, and I sense trouble if you really apply that as a rule. There are many words in that sentence. So you can't just say that "whenever you find a word" it means anything at all. A verb has to agree with its subject. One extension is. Two extensions are. Simple as that.
    – RegDwigнt
    Oct 28, 2014 at 10:58
  • even if I'm not referring to every single extension, and referring to all the extensions as a whole?
    – 7kemZmani
    Oct 28, 2014 at 10:59

1 Answer 1


Writing are is correct. You use are because the world extensions is plural. If it wasn't (extension) you would have used is.

It doesn't matter if you are referring to every single extensions or to all of them together in this case.

You must use are, that's the rule :)

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