A number of

This is interesting timing because, as I said in my last post, I wanted to discuss the issue of what seems like a collective noun, "a number of," and whether it should be "is" or "are." And this week, someone was writing something at work, and he asked me if he should say "a number of is or are." After we had a brief conversation about it, I told him it should be "a number is," but now I realized I was wrong (but maybe it was right for the context? I don't remember what the sentence was; it made sense at the time).

I encounter "number of" many times in my work (usually "the number of") and saw "a number of" recently in something I had to copy edit. I hesitated when I saw that because it's very tempting to use "is" due to focusing on the first part of the sentence, which is "a number." But the Oxford Living Dictionary says it's supposed to be are: "A number of people are waiting for the bus." But that makes sense to me, too, because "people" is close to "are" and it sounds right.

But it's not enough for something to just "sound right" when writing or editing, because it's more formal than speaking, and we can usually break the rules in spoken English.

According to Editage, "Do not be misled by the indefinite article a in that expression: the expression is always used to indicate more than one of something and therefore takes a plural noun and a plural verb."

They also discuss "the number of," and now that I'm thinking of it, I see it way more often, which pretty much everyone says should be singular, such as "the number of plants in each pot was 25." In that case I've been right, and I'm glad my instincts were correct.

After much thought and online searching, I think I found the best explanation for this phrase at ESL Library: "a number of means many...it is serving the same role in the sentence as a quantifier such as 'many,' 'a lot of,' 'lots of,' 'hundreds of,' etc."

So from now on, I won't think twice about making "a number of" plural! I feel like I've read the equivalent of a booklet on that topic!