A: I’ve often said that a writer who knows the rules has a right to break them. And Wallace certainly earned the right to break a few rules.
Generally, however, “couple of” is standard usage before a plural noun, which is what I advise in my book Woe Is I: “a couple of changes,” not “a couple changes.” Better English – that is, more formal English – demands the “of.”
The reason for this is that “couple” is traditionally regarded as a noun, so it needs a preposition to link it to another noun, like “changes.” Except in informal English, it’s not an adjective, like “two” in the expression “two changes.” For a parallel example, think of the word “pair,” as in “a pair of shoes,” or “brace,” as in “a brace of pheasants.”
The American Heritage Dictionary of the English Language (4th ed.) agrees with this, but Merriam-Webster’s Collegiate Dictionary (11th ed.) is more flexible. M-W accepts the use of “couple” as an adjective (without “of”) in casual usage.
Merriam-Webster’s considers dropping the “of” to be “an Americanism, common in speech and in writing that is not meant to be formal or elevated,” and says this informal usage is especially common before “periods of time (a couple weeks) and numbers (a couple hundred, a couple dozen).”
I agree that “couple” alone is often enough before numbers and periods of time, but I still advise “couple of” before ordinary plural nouns except in very relaxed usage. Dropping “of” conveys a folksiness that you might not want in your writing or speech.
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