Commas between Compound Predicates

We learn from CMOS 6.23 that “a comma is not normally used to separate a two-part compound predicate joined by a coordinating conjunction.” In other words, when the subject isn’t repeated after a word like “and” or “but” in a compound sentence, a comma is usually omitted:

We walked to the tracks and waited for the train to appear.

This is the opposite of the rule stated in CMOS 6.22. When the subject is repeated, or when there are two different subjects, a comma usually precedes the conjunction:

We walked to the tracks, and we waited for the train to appear. [The subject “we” is repeated.]

We walked to the tracks, and the train came into view. [There are two subjects: “we” and “the train.”]

Of the myriad rules for using commas in sentences, the one that says to omit a comma between compound predicates but not between independent clauses ranks high on the scale of arbitrariness. The presence or absence of such a comma rarely changes the meaning of a sentence.

Readers, however, are almost always helped by a consistent, predictable approach to marking sentence structure. And that’s why most editors working with formal, expository prose are relatively strict about enforcing this rule, arbitrary or not.

In fiction and other forms of creative writing, it’s a different story. In an earlier post, I considered creative exceptions to commas between independent clauses. In this one, let’s explore the related case of commas (or their absence) between compound predicates.

The Omitted Subject

First, writers and editors should know that it is never strictly wrong to place a comma between compound predicates joined by a coordinating conjunction. In the first example at the top of this post, the repetition of the subject is understood from context and mentally supplied by the reader as needed. Seen this way, a comma looks less like a mistake and more like a potentially useful remnant:

We walked to the tracks, and [we] waited for the train to appear.

And such a comma can be helpful to readers—for example, to emphasize the sequence of events without repeating the subject, or to help readers sort out a particularly long or complex sentence. But again, in formal prose these commas are routinely omitted. In fact, CMOS currently recommends a comma in such cases only where ambiguity threatens, as in this classic example:

She recognized the man who entered the room, and gasped.

We need that comma before “and” if we are to understand from the sentence alone (rather than from its surrounding context) that it was the subject of the sentence (“she”) who gasped and not the man.

That’s a rare scenario; most sentences don’t end with one person entering a room and another gasping. But a comma can be useful even when a sentence is clear without one, particularly in creative writing.

Comma before “And”

A comma suggests a pause or a shift of some kind. When “and” joins two predicates, a comma can provide subtle emphasis for the second one—by suggesting that the words following the conjunction are an afterthought, or by slowing the reader down and emphasizing the sequence of events. For example,

I printed out a year’s worth of crossword puzzles, and will play them when I have time.*

But commas aren’t very good at signaling an afterthought or similar shift all by themselves. If you truly want to draw attention to the information in the second predicate, use a dash or parentheses instead—or start a new sentence:

I printed out a year’s worth of crossword puzzles—and will play them when I have time.

I printed out a year’s worth of crossword puzzles (and will play them when I have time).

I printed out a year’s worth of crossword puzzles. I’ll play them when I have time.

The second half of the original sentence has now been transformed into an afterthought or additional consideration—in a way that can’t be missed.

Comma before “But” or “Or”

After an “and” readers expect more of the same, which is why a comma alone may not be strong enough to alter how readers take in the sentence. A “but,” on the other hand, introduces a shift—toward an antithetical or opposing thought—all by itself.

Because readers already understand this as a shift, a comma might seem even less necessary than it usually does. But if emphasis is what you’re aiming for, it can play a reinforcing role:

I printed out a year’s worth of crossword puzzles, but won’t play them until I have time.

Like the comma before “and” in the previous section, this one would normally be omitted. But in creative prose, and depending on the author’s style, it can sometimes stay where it is.

The conjunction “or,” which introduces an alternative, is a hair stronger than “but.” It provides a correspondingly bigger opportunity for adding emphasis:

I printed out a year’s worth of crossword puzzles, or would have printed them out eventually.

That comma encourages the reader to notice this as a moment of uncertainty or ambiguity rather than as a case of simple alternatives. In creative writing such moments are common, and authors or editors who want to omit the comma—or to upgrade it to a dash or parentheses (or start a new sentence)—should consider not only the meaning of the sentence but also the author’s style. Especially if the author tends to use a lot of discretionary commas (in what is sometimes referred to as a closely punctuated style; an open style features fewer such commas), that comma before “or” is better left where it is.

Length and Complexity

The length and complexity of a sentence also play a role. The following sentence doesn’t need a comma, strictly speaking, but it helps:

Electra alternated between keyboards and bass in three consecutive sold-out shows in the middle of the week, and sang every lead.

That sentence could be rewritten for greater clarity. But as is, the comma before “and” will help readers differentiate the long first predicate from the shorter second one. If it were to be read aloud—a more likely scenario with a novel or a story (or a poem) than with a scholarly journal article or historical monograph—that comma would help readers take a breath.

On the page, too, we need time to process what we read, and commas can help with that.†

A Poem . . .

Real-world examples of commas between compound predicates aren’t hard to find. Practically any piece of creative writing will yield one sooner or later. But rather than hunting for these subtle markers in the pages of a long novel, let’s start with something obvious.

Whitman’s “Song of Myself”—written in the form of verse but using conventional sentence structure and punctuation—includes the following famous first stanza: “I celebrate myself, and sing myself, / And what I assume you shall assume, / For every atom belonging to me as good belongs to you.” In early editions (before 1881), “and sing myself” had yet to appear, leaving a short first line: “I celebrate myself, / And what I assume . . .”

The opening lines from the 1855 edition of Walt Whitman’s Leaves of Grass.

The end-of-line commas were replaced in an interim edition with semicolons; later versions restore the commas—and add the now-famous words.

“Song of Myself,” from the 1891–92 edition of Leaves of Grass.

Is that comma before “and sing myself” needed? Let’s say I like oranges in any form, solid or liquid: “I eat them and drink them.” Subject-verb-object followed by a coordinating conjunction followed by a different verb and then the same objective pronoun from the first part of the sentence. In other words, a sentence with a compound predicate modeled after Whitman. The verdict? No comma.

But that normally superfluous comma creates a pause—“I celebrate myself, and sing myself”—that allows us to appreciate those three additional words as clarifying and amplifying the three that come before, transforming Whitman’s earlier opening from an ordinary statement of self-regard to the announcement of a major poet.

. . . and a Story

Today, creative writers continue to have this option. The New Yorker, famous for its comma-heavy editing, makes this immediately apparent. Take “The Rivals,” a new story by Andrea Lee published in the first issue of 2021 and set in Madagascar. The story is conventionally structured and closely punctuated. Commas generally appear between independent clauses joined by a coordinating conjunction; but they also often appear between compound predicates—so frequently that it becomes the rule rather than the exception.

These commas tend to intervene in any sentence with the least complexity—for example, when there is a third predicate and additional conjunctions: “She could type and use a computer, and spoke French and Italian.” This sets up a precedent for using predicate-separating commas in any complex sentence:

Occasionally, she typed a document for Pianon, and sometimes, in the tone of a schoolmistress, translated for him an obscure term in Sakalava dialect, or explained some custom, like why it was fady for certain young girls to eat chicken.‡

Note the commas after the name “Pianon” and the word “dialect,” respectively. The subject of the sentence, “she,” is not repeated, so these commas would be removed under strict Chicago style. You could still choose to set off “sometimes,” but then the comma would follow the conjunction (“and, sometimes, . . .”). But that’s optional, as is the comma after the one-word adverbial introduction “Occasionally” (see CMOS 6.31).

Leaving all those commas out, this is what a Chicago-style revision would look like:

Occasionally she typed a document for Pianon and sometimes, in the tone of a schoolmistress, translated for him an obscure term in Sakalava dialect or explained some custom, like why it was fady for certain young girls to eat chicken.

This sparer style works well, but if you removed those commas, you’d be obligated to go back and reread the story to make sure comma usage elsewhere is consistent—except for any exceptions that seem warranted for the sake of clarity, emphasis, or rhythm. It’s no exaggeration to say that next to logic, consistency is the most important goal in editing. You might even say that consistency creates its own logic. Once you’ve established that commas will appear between compound predicates in most instances (or that they won’t), you can run with that decision as “correct for this piece.”

* * *

The New Yorker story proves that these commas are both arbitrary and subtle. Or maybe not arbitrary—not if they are used in some way that readers will appreciate as either consistent or intentional. But they are subtle.

Not that subtle equals bad. In creative writing, subtlety and nuance can work to your advantage. Authors and editors who pay close attention to their own style and work within its logic will be rewarded by attentive readers who haven’t been pulled out of a story or a poem by odd or random-seeming choices. And there’s nothing subtle about that.

* The comma in that sentence, as in most of the examples in this post that feature a compound predicate, would be flagged by Microsoft Word’s grammar checker as an error. As with many of Word’s suggestions, you can take this one as a consideration rather than as a mandate.

† We see the reverse with independent clauses joined by a coordinating conjunction, a scenario that normally calls for a comma. If the clauses are short and closely related, the comma can be omitted: “Electra played the guitar and Tambora sang” (see CMOS 6.22). That sentence is so easy to digest that a comma, whatever else its merits, simply isn’t needed.

‡ As suggested by the context, the word fady means “taboo.”

Train photo by Josh Hallett, licensed under CC BY 2.0. Page images from Leaves of Grass are from the Walt Whitman Archive.

Fiction+ posts at Shop Talk reflect the opinions of its authors and not necessarily those of The Chicago Manual of Style or the University of Chicago Press.

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Russell Harper (@cpyeditor) is editor of The Chicago Manual of Style Online Q&A and was the principal reviser of the last two editions of The Chicago Manual of Style. He also contributed to the revisions of the last two editions of Kate L. Turabian’s A Manual for Writers of Research Papers, Theses, and Dissertations.