From The Week:
There is a myriad of ways we can express quantities in English, but there are just a couple words that are much in dispute.
Wait. Should that be “there are myriad ways” and “just a couple of words”?
Those are the two words much in dispute: myriad and couple. But we ought to just relax and let them go. They’re only sliding down the same slope as many words have before them, and still more might after them: the slippery slope from noun to quantifier.
What’s a quantifier? It’s a kind of word not everyone knows exists. Many people — including some who write usage guides and dictionaries — think there are nouns, and there are adjectives, and everything that modifies a noun is an adjective. It’s tidy, but it’s not true, and it leads to some silly mistakes.
First of all, numbers aren’t adjectives. They’re not! We know this because they don’t behave exactly like adjectives. For example, I can say “soft red pillows” and “the pillows are soft and red,” but if I say “three soft red pillows,” I can’t say “the pillows are three, soft, and red” — and I most certainly can’t say “the pillows are very three” even though I can say they are “very soft and red.” Also, I can say “a pink balloon” but I can’t say “a one balloon.” (After all, a comes from one.)
But not all words that express quantities are numbers. Even some numbers aren’t like other numbers. Consider: I can say “a thousand balloons,” “a few thousand balloons,” and “many thousands of balloons,” but I wouldn’t say “a nine balloons,” “a few nine balloons,” or “many nines of balloons” (unless I meant many nine-packs, in which case nine has become a noun standing for “nine-pack”).
That’s because thousand started out as a noun and, a long time ago, slid down the slope to becoming a quantifier. So did hundred. So did dozen. And that’s the slope that couple and myriad are on right now.
When these words were nouns, they behaved like nouns, pluralizing, taking a singular verb when single, and needing an of to attach them to another noun. That’s right: “a thousand of cattle,” “two millions of pounds,” “several dozens of eggs.” We still sometimes use dozen like this when referring to cartons. These quantifiers still show the marks of their noun past: “There were a hundred cats,” not “there were hundred cats” (compare “there were nine cats”); “thousands of dogs” and “scores of years” but not “fifties of dogs” or “nines of years.” Quantifiers that were once nouns can still be used at least sometimes as nouns (depending in part on how far down the slope they’ve slid). But the rest of the time they’re not behaving like nouns — but not like adjectives either.
. . . .
Myriad is not nearly as common a word as couple, but it has more ways it can be used. I won’t say there are myriad ways you can use it, or a myriad ways you can use it, or even a myriad of ways you can use it — or that thereis a myriad of ways — but there are at least those four ways. It started as a noun, of course, meaning “group of 10,000,” borrowed from Greek by way of Latin. It arrived in English in the 1500s, and by the 1600s it was already being used on occasion as a quantifier, both with and without a. It slipped down the slope quickly, no doubt at least in part because of its magnitude — when many just isn’t big enough, myriad serves nicely. But it’s stayed in use at all the stages of the slope: “a myriad of ways is,” “a myriad of ways are,” “a myriad ways are,” “myriad ways are.” Since it’s been used all these ways for centuries, there’s no reason not to keep using it however we want, choosing according to what works best in the context.
Link to the rest at The Week and thanks to Matthew for the tip.