I have a friend who regularly calls and, the moment I answer, bursts into a sentence like this: "So did you hear that they gave him the thing and after they did she saw it and said that they didn't want it?"
Then, for about five minutes, I'm forced to play "Identify the Pronoun."
Who's they? Gave something to who? What did they give him? Who's the woman you mentioned?
My friend is a great person. Very interesting and informed and generous of heart. But if it were up to me, her license to operate a pronoun would be revoked.
In casual conversation, there's no common term for this problem, except maybe "Stop talking or my head is going to explode." But in writing, there's a more specific and more helpful term: unclear antecedent.
You can probably guess what an antecedent is. It's a noun that appeared earlier in the text and that a pronoun is now referring to.
Take, for example, "Jane gazed at her reflection." Is there any doubt who is referred to with the pronoun "her"? It's Jane, of course. We know that because we stated who we were talking about earlier in the sentence.
But now consider this sentence: "Jane and Rose gazed at her reflection in the mirror." Whose reflection? Jane's or Rose's?
It's clear from the singular pronoun "her" that it can only be one of them. But, barring the possibility that a prior sentence tipped us off, we have no way of knowing who "her" refers to.
That's an unclear antecedent — a problem far more common than you might guess. As a copy editor, I encounter unclear antecedents often. In many cases I'm powerless to fix them.
After all, the problem is that it's unclear who is or what is being referred to. If I insert "Jane's" in place of "her," there's a 50-50 chance I've just made an unclear sentence into something worse: a factually incorrect sentence.
Unclear antecedents seem most common with personal pronouns. The subject forms (he, she, we), object forms (him, her, us) and possessive determiner forms (his, her, our) are equally abused.
But other types of pronouns get used without clear antecedents, too.
"I know there's a lot to say, which isn't necessarily important." In this sentence, "which" is a pronoun. Like all pronouns, it's supposed to refer to something known to the reader. But here, you can't really know what it refers to.
Compare that to: "I know you read the email, which wasn't very helpful." Here, "which" clearly refers to the email.
A pronoun's antecedent can be left implied. But only when the reader will understand.
"There are too many people here, which is why we're leaving." Notice how in this sentence there's no specific noun referred to by "which." But that's not a problem because our pronoun makes reference to something the reader can easily figure out.
"The fact that there are too many people here" is why they're leaving. "That crowds" are why they're leaving. The reader can easily figure out that "which" represents something along those lines.
To avoid unclear antecedents, you must be cognizant of what your reader already knows and what she doesn't. That can be tough.
The act of writing is essentially taking something that's in your own head and putting it in someone else's. To do that, you must make a number of calculations about what needs to be explained and what doesn't.
For example, in the first sentence of this column when I mentioned I have a friend who regularly "calls," I was counting on you to know I meant a phone call and not an in-person social call or some kind of bird call.
We make countless calculations of this nature every time we communicate with each other. Some people are just better at it than others.