If I want to ask about some notion mentioning it in plural? Should I use "is" or "are"?

What is coroutines?


What are coroutines?

or better avoid such a forms and be strightforward

What is coroutine?

Intuitively I use "is" like it single notion which just described as word in plural form. But is there a rule for such a case? Or what the form is preferable?

closed as off-topic by Edwin Ashworth, David, jimm101, user067531, Drew Jan 31 '18 at 19:15

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  • Better to use 'What are coroutines?' or 'What is a coroutine?' – Kate Bunting Jan 31 '18 at 8:52

The verb should match the noun. 'Coroutines' is plural, so the verb should be plural.

What are coroutines?

The singular form works too, but needs the indefinite article:

What is a coroutine?

  • I think the downvote needs an explanation. – DJClayworth Jan 31 '18 at 14:26

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