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A source says that the word "each" should always be followed by a singular noun, but however I look at it in this sentence it just doesn't seem to fit:

foo comprises of multiple binary programs that each performs a single task.

Should it be "performs" or "perform"?

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Define Should in the question? –  user14070 May 10 '12 at 14:33
    
You mean either consists of or else just plain comprisesnot “comprises of” with an extra “of”, as this does not make sense and is not English. –  tchrist Dec 20 at 1:51

4 Answers 4

Each in phrases like each battery is singular; the verb you use in that cases is singular.

Each battery is in a separate compartment.

Vice versa, in sentences like the following the verb is plural.

They each have their own personality.
Foo comprises multiple binary programs that each perform a single task.

Subject and verb must agree in number; in multiple binary programs that each perform a single task, the subject is multiple binary programs, which is plural, and the verb needs to be plural too (perform).

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You have arrived at the correct answer, but your explanation does not strike at the real issue: Why is it so? "Vice versa, in sentences like the following the verb is plural. They each have their own personality. Foo comprises multiple binary programs that each perform a single task." The explanation is that each is not being used as a pronoun, as most folks erroneously assume, so perform must agree with the relative pronoun "that". –  ScotM Dec 20 at 17:51

Each is always singular. You are talking about how “each program is” doing one thing. Or how “each of these is” doing one thing. Both formulations are allowed, and in either case, it is singular. Only. That means that all of these are inadmissibly wrong — or alternately, each of these is inadmissibly wrong:

  • each ∗programs ∗are
  • each program ∗are
  • each ∗programs is
  • each of these programs ∗are

None of that is English.

Well, not correct English, that is. The OED says:

With reference to a sb. going before, or followed by of. Sometimes incorrectly with pl. vb.

All the citations of the incorrect use are also quite old.

No complex analysis is needed here: each, like every, is always singular, even when it is distributing a plural subject.

Also, “foo comprises of ” is also not English. It needs to be “foo comprises”. I know people who never, ever say comprise for fear of using it wrong, or worse, of being miscorrected. There might be betters words here, like consists of.

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As a pronoun, "each" is always singular, but in the sentence the OP constructed, each is not being used as a pronoun. –  ScotM Dec 20 at 17:49

But the AHDEL does give a complex analysis of structures using each following a plural subject - and one that is in line with kiamlaluno's second example, and with which I agree. Admittedly there is not an example parallel to the original with the that-clause cited, but thesaurus.com has individually and each as synonyms in this usage, and obviously Foo comprises multiple binary programs that individually perform a single task needs plural verb concord. Whether the object should be singular or plural is a different matter.

I'd probably use:

Foo comprises multiple binary programs: each performs a single task.

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Ignoring all other errors, we have the illusion of an internal conflict in this sentence. Both "that" and "each" seem to funcion as the subject for the verb "perform",

BUT in this sentence, "each" is not functioning as a pronoun. Some would argue it is functioning as an adjective modifying the relative pronoun "that", which is the subject of the relative clause. Others would argue it is functioning as an adverb modifying "perform". Either way, "each" is neither singular nor plural. See Each.

Tabulating functions:

Subject: foo

Verb: comprises [sic]

Prepositional phrase: of multiple binary programs

Relative clause: (referent programs) that each perform a single task

In an additional test, the sentence would make perfect sense without the word "each":

foo comprises of multiple binary programs that perform a single task.

Therefore, ignoring other errors, the correct verb form would be perform.

"foo comprises of multiple binary programs that each perform a single task."

That may be awkward style and improper use of the word "comprise", but otherwise it is the correct grammar for "each".

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protected by RegDwigнt Jul 3 '12 at 19:04

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