What Is Subject-Complement Agreement?

How to use it, and how not to use it.

Bonnie Mills, Writing for
5-minute read
Episode #176


Grammar Girl here.

In today’s episode we’re going to answer some bizarre and puzzling questions: Can two people share a life? Can two writers share a neck? How many heads does a person have? How many wives do certain men have?

Today's guest-writer, Bonnie Trenga, tells us that the issue at hand is what’s called subject-complement agreement. A complement—that’s p-l-i-m-e-n-t—is a noun that subjectcomplementcompletes meaning (1). Take the sentence “She is my sister.” The words “my sister” are the complement. There’s no agreement problem in that sentence, it's all singular, but what about a sentence like this: “The two girls ate their sandwich”? Does this mean the girls shared one sandwich or did they each have a sandwich?

Tricky Sentences

A few confused listeners have brought up such tricky sentences for us to parse. For example, Drue R. asks whether it would be proper to write “They visited each other's shrine, or “They visited each other's shrines.”

And Kathleen M., poses these questions: Is it “We help clients get the most out of their life” or “We help clients get the most out of their lives”? What about “The writers complained that their neck was sore” or “The writers complained that their necks were sore”?

Those are all good questions that forced us to dig deeply within many grammar resources, hoping they would provide an answer. Most, unfortunately, don’t address this subject.

Obvious Errors

We’re lucky, though, that two grammar authorities do have an answer to these puzzling questions. We'll start simply and work our way up to the more difficult questions.

Our old favorite, Garner's Modern American Usage (2), points out that a common mistake in American and British English is to “attribute one result to two separate subjects, when logically a separate result necessarily occurred with each subject.” So the sentence “He was hit by a pitch two times” is wrong because the batter was hit by two separate pitches, not one pitch two times. You should say, “He was hit by two pitches.”

In the same vein, the sentence “Strip malls may be an eyesore, but they sure are convenient” would be incorrect. In this sentence, the subject is “strip malls,” which is plural, but the complement is the singular word “eyesore.” This is an obvious error that’s easy to fix; just make everything plural: “Strip malls may be eyesoreS, but they sure are convenient.”

Collective Nouns as Complements

Other sentences with a plural subject might not be so easy. What if the complement is a collective noun that you can’t make plural, such as “dignity”? Should you say, “The warriors retained their dignities” or “their dignity”? Well, the answer seems obvious here: “dignities” doesn’t make sense. So the rule with collective nouns that are complements is to keep the complement singular, even with a plural subject (2).

Ambiguous Sentences

Now let’s move into trickier territory, where we encounter ambiguous sentences. Remember our tricky questions about people with more than one neck or more than one life? Here's another one. Should it be “They shook their head,” or “They shook their heads”?

Common sense tells us that people have only one head, but we run into a problem no matter what we say. If we use “heads,” we suggest the ridiculous possibility that they have two heads; if we use “head,” we suggest that they are sharing a head—also ridiculous. 

We run into the same problem with the sentence “Both men relied heavily on their wives” (3). If we wrote “Both men relied heavily on their wife,” that would suggest the men share a wife; if we say, “wives,” that suggests each man has more than one wife. It’s a lose-lose situation. As Garner's states, “Sometimes neither the singular nor plural can prevent ambiguity” (2). So we turn to the second grammar source we’re consulting today, Barbara Walraff’s Word Court.

Abstract and Countable Complements

Ms. Walraff presents a number of scenarios and a number of answers. One kind of sentence she discusses is “They taught school,” in which “school” is a singular complement. It appears not to match the plural subject, until we consider that “school” is used in an abstract manner. It wouldn’t make sense to say, “They taught schools.” Heads, necks, and wives, on the other hand, are not abstract. They are countable (and people usually have one of each).

Let’s take the sentence “The writers complained that their neck was sore” and see what Ms. Walraff would say about it. Unlike most grammarians, who are uptight about rules and who want things to be right, she tells us not to worry about it. She states, “It is usually either obvious or beside the point how many of the things are to be paired with the individuals in the subject, and then one needn’t scruple to use the plural…. This is the rule, it seems to me, that really applies to your wives—and your heads.” She seems to approve of using the singular “neck” after the plural “they.” If I had to pick between “their neck” and “their necks,” though, I would probably pick “necks.” It just sounds better to me: “Their necks are sore.” Perhaps it’s a matter of personal taste.

Solutions to the Conundrum

Ms. Walraff spends a couple of pages on this topic and suggests three solutions to this conundrum. The first, as we’ve mentioned, is not to worry about the situation too much. Most subject-complement agreement problems are “innocuous,” she says. OK, we can all relax about it. The grammar police will not show up on our doorsteps. The second is to consider rewriting the sentence, and the third is to add more information that indicates how many of an item you’re talking about. Perhaps in this case we could rewrite it like this: “Both writers had sore necks,” or we could add information by stating, “Both writers complained that they had neck aches caused by staring out their windows too long.”


If we look back at the pairs of sentences that readers were asking about, can we now tell which one in each pair is right? You’d probably be safe using either way, but to avoid crazy-sounding sentences, it’s best to follow Ms. Walraff’s advice: relax, and then reword your sentences or give other clues about how many items you’re talking about. And, as Ms. Walraff warns, if “carefully matching numbers results in ridiculous wording, don’t do it.”

The Curious Case of the Misplaced Modifier

This podcast was written by Bonnie Trenga, author of The Curious Case of the Misplaced Modifier, who blogs at sentencesleuth.blogspot.com, and I'm Mignon Fogarty, the author of the paperback book Grammar Girl's Quick and Dirty Tips for Better Writing.


Finally, if you want to get Grammar Girl and other great shows from Quick and Dirty Tips streamed to your iPhone (and now your BlackBerry too) try Stitcher free today at stitcher.com.

That's all. Thank for listening.


1. Lutz, G. and  Stevenson, D. Grammar Desk Reference. Cincinnati: Writer's Digest Books, 2005, p. 13.
2. Garner, B. Garner's Modern American Usage. Oxford: Oxford University Press, 2003, p. 175.
3. Walraff, Barbara. Word Court. Orlando: Harcourt, 2000, pp. 127-8.


About the Author

Bonnie Mills, Writing for Grammar Girl

Bonnie Mills has been a copyeditor since 1996.