When we use a common countable noun in singular in general to represent the whole class it is preceded by the definite article the. As-

The horse runs fast.

But where the noun in a sentence is preceded by an adjective which article should be used there before that adjective a or the. As-

a common man knows everything


The common man knows everything.

  • Possible duplicate of The confusion between "The" or "A" article I would say that the indefinite article is non-idiomatic for A common man knows everything, but that might just be because common man isn't really an established collocation for any contexts other than the common man = the man on the Clapham omnibus = the [ordinary] man in the street,... Commented Apr 13, 2018 at 16:46

1 Answer 1


First, note that this use ("the" with a singular to denote a class) is pretty old-fashioned. You won't find it very much in contemporary writing, and not at all in speech. The plural "Horses run fast" is much more common now.

And that goes over to the case with the adjective. "The common man" as a class is very formal or literary (I immediately think of Aaron Copland's musical piece Fanfare for the common man).

I'm not sure about "A common man" in that way. I think it is possible, but for me it sets up an expectation that you are going to distinguish a common man from some other kind of man. Again I think the plural (probably "common people" rather than "common men", unless you are specifically talking about only males) is more likely.

  • Well put and succinct.
    – Lambie
    Commented Apr 13, 2018 at 16:26

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