Sometimes it’s the wrong rhythm, sometimes the wrong meaning
It’s easy to get the idea, depending on what guidelines you’ve read (and who you’ve worked with), that you should always use a comma between two independent clauses joined by a coordinating conjunction (and, but, or/nor, for, yet, so).
Nothing could be further from the truth.
Why this comma?
One of the purposes of the comma is to balance in parallel elements of like meaning and form. We see that in the commas that separate coordinate adjectives before the noun, in the commas used to separate items in a series, and of course in this comma used between two independent clauses joined to form a compound sentence.
However, while the comma between coordinate adjectives aids in comprehension and the comma in a series is there for rhythm and balance (and sometimes to prevent misreading), the comma between two independent clauses — most particularly when the conjunction is and or or — is more about convention. It’s there, to some extent, to assist reading. It’s there also to call out this balanced relationship between the two clauses. Using it represents the baseline and neutral approach. If the structure in question really is just the two independent clauses to be taken and weighed together — without other relationships at work across both clauses — then you can almost never go wrong using it.
But even where it might be used in perfect compliance with the vanilla guideline, in some writing modes you have choices. There are also circumstances that in any context call for the suppression of this comma in recognition of an overarching structure that governs the compound clauses.
Note that this applies most especially when the connectors are and or or, less frequently with but, and generally not at all with for.
Omitting it by choice
If you’re writing fiction or narrative nonfiction, then you can often omit this comma purely in pursuit of a particular style and voice. Typically, you’d not do that where misreading might occur, but if you’re adopting a style of writing that avoids this comma to the extreme, then even the possibility of misreading might not deter you. Your decision would have to do purely with rhythm and pacing, with the poetry of the language on the page, and the intent of the words.
Even in pieces that use this conventional comma quite freely, there may be particular sentences where the effect you’re going for calls for leaving it out. For those of you writing in environments that follow The Chicago Manual of Style, take heart! The manual gives its blessing to this flexible and stylistic approach to commas in Commas and Independent Clauses: A Creative Opening on the CMOS Shop Talk site. Keep in mind, too, that CMOS applies most comfortably to nonfiction trade (most particularly standard, nonnarrative nonfiction) within the publishing industry, to academic writing, and (minus aspects such as foot- or endnotes) to corporate contexts.
Example
It’s hard to tell because we are weak from hunger and sleeplessness and the blunt passing through our hands and all we want is home.
“The November We Are Fifteen,” Lydia Armstrong
The Best Small Fictions 2017
This piece is written in bursts of single-sentence paragraphs, all with this same style. Lots of coordination (compound structures, of both phrases and sentences), no commas. It’s a deliberate style of writing, a distinctive voice — a way of painting with the words that is wholly this author’s and that works well in this piece.
This is all fine. It’s fiction: art (image, emotion, experience) conjured from words.
Example
Gary drank single malt in the night, out on the porch that leaned toward the ocean. His mother, distracted, had shut off the floodlights and he did not protest against the dark.
“Currents,” Hannah Bottomy
Flash Fiction Forward (2006)
In that second sentence, not bringing in the comma between those two independent clauses serves to more clearly highlight the adjective that’s set off in commas (“distracted”), while drawing together the two main actions. Even were the remainder of the piece to use this conventional comma, it would be fine to leave it out here.
Example
Now my father is in the car, shouting for me to drive away. There will be time enough for silence and rest. We are both stupid with smiles and he is shouting, “Drive fast, drive fast.“
“Wallet,” Allen Woodman
Micro Fiction: An Anthology of Really Short Stories (1996)
In the third sentence, with the deliberate omission of the comma, the two short independent clauses are grouped more closely together and the line of dialogue is highlighted. Again, careful decision-making. Punctuation falling in line with the desired effect.
Example
It takes the whole morning to prepare perch chowder and all afternoon to cook it, so no fishing today. Sit on the floor and play Legos together, the Legos you had when you were his age. The bare house begins to warm and smells of cream and butter and you think: this is a new memory, just the two of us.
“Ways to Prepare White Perch,” Jennifer Genest
Winner of the 2014 Ryan R. Gibbs Award for Short Fiction
New Delta Review
In the third sentence, a similar effect as with the previous example: the initial thoughts are brought together — the more so as the very short independent clause (“you think”) is preceded by a compound predicate (“begins to warm and smells . . .”) that itself contains another compound (“of cream and butter”), so there’s the effect of one thing tumbling over the other. And then what follows the colon is more clearly set off.
Example
Now in the early evening the sun is flashing everything in gold. It bathes the blunt gray rocks that loom yearningly out toward Europe and it touches upon the stunted spruce and the low-lying lichens and the delicate hardy ferns and the ganglia-rooted moss and the tiny tough rock cranberries. The gray and slanting rain squalls have swept in from the sea and then departed with all the suddenness of surprise marauders. Everything before them and beneath them has been rapidly, briefly, and thoroughly drenched and now the clear droplets catch and hold the sun’s infusion in a myriad of rainbow colors.
“The Lost Salt Gift of Blood,” Alistair MacLeod
From a collection of short stories of the same name (1988)
Omitting the comma between the independent clauses can give the prose the feel of undifferentiated languor, as here, or it can impart a kind of breathless quality, as demonstrated in some of the other examples.
Omitting it by reason of structure
If you’re writing what’s sometimes called informational nonfiction, sometimes “prescriptive” nonfiction — writing that guides, teaches, or informs — then you’re generally going to use this comma. If you’re writing fiction or narrative nonfiction, then you’ll use it or not as supports the effect you’re going for in individual sentences or perhaps across the entire piece.
But whatever you’re writing, there’s a widely accepted foundational circumstance in which it’s entirely optional, and so in this case you would be guided by rhythm and intent in deciding whether to use it or not. The Chicago Manual of Style makes a brief reference to this circumstance at ¶6.22.
And there are a handful of other circumstances in which you’d not use it, as to do so would be to buck the overarching structure of the sentence. These structures are canvassed in The Copyeditor’s Handbook by Amy Einsohn and Marilyn Schwartz (a standard copyediting reference) and The Handbook of Good English by New York publishing house editor Edward D. Johnson. And of course in many other writing style guides that explore beyond the basics into nuance.
An aside: The examples from here to the end reflect a specific writing environment. Other fiction examples, and also examples from works of nonfiction, to come.
Short, closely connected Independent clauses
This is the most basic principle: if the two independent clauses are short and closely connected, you need not use the comma. It’s optional. And that’s in any writing environment, even those where this comma is generally used without question.
Examples
The dragon snorted a puff of smoke and she flinched.
Something by the tree caught her attention and she stepped closer.
Just close your eyes and share with them instead of me.
There are multiple types of neurotransmitters and not all are excitatory.
Omitting the comma brings the two thoughts together, coupling them more closely, emphasizing not the separation but the conjunction of the two.
Conversely . . .
The dragon snorted a puff of smoke, and she flinched.
Something by the tree caught her attention, and she stepped closer.
Just close your eyes, and share with them instead of me.
There are multiple types of neurotransmitters, and not all are excitatory.
Using the comma introduces a pause and so changes the rhythm of the sentence, adding emphasis both before and after. In other words, the comma serves to separate the two thoughts.
closely connected Independent clauses interrupted by another structure
When an intervening clause or phrase interrupts two such short (or even not so short) independent clauses, that close conjunction between them — enhanced by the lack of a comma between them — becomes important for another reason: it highlights the relationship of the information in the interrupting piece with the information of the base sentence.
It is best in these cases to use no additional comma but only those two that set off the intervening piece.
Example
Her wrist joined her hand and then, as if she were being painted into the scene, she became visible.
“The Unseen,” Kaitlyn Carter Brown
Sensational: Havok Season Four
The comma between the independent clauses, not necessary here for comprehension, is suppressed for rhythm and pacing. Suppressing it gives the phrase enclosed in commas — now the only commas in the construction — greater weight, which in turns gives the sentence greater lyricism.
Even were the compound to appear without that intervening piece, it would not need the comma:
Her wrist joined her hand and then she became visible.
You could include it: the comma would not be wrong here, naturally. But, likewise, it is not absolutely required, even by convention. You would choose the comma or not depending upon the effect you were going for.
closely connected Independent clauses preceded or followed by another related structure
Sometimes two short (or maybe kind of medium length) and closely related independent clauses are not interrupted with a phrase or clause, but instead one precedes or follows. You would include the comma between the two independent clauses or not depending upon the desired effect of the whole.
If the two clauses would be better seen as a unit, against which the other phrase or clause is contrasted, you would not use a comma between them.
Example
I tried crying out, but the blade against my mouth tightened and my scream became a grunt.
“Beware, Said the Man of Straw,” Jim Doran
Havok Online
Here, the opening clause sets the scene for, and is juxtaposed with, the entirety of what follows in the sentence. With the one comma only, the one that delineates this overarching structure, that relationship is highlighted. If another comma were to appear in the sentence, instead of the two actions we’re to understand at odds with each other (his struggle to cry out, his inability to do so), we would now see a series.
It would not be absolutely wrong to place a comma here, that is, it violates no rule of grammar, but neither is it wrong to omit it. The choice then is stylistic, semantic. It has to do with rhythm and pacing — and meaning. The informed choice would be to leave it out.
If these two independent clauses currently framed within a larger structure were themselves to be pulled out into a separate structure — “The blade tightened against my throat and my scream became a grunt” — the comma between those two clauses would be entirely optional. You’d use it or not depending upon the rhythm and pacing you were looking for.
Note that not all commas are similarly up for debate. Many follow directly from the grammar of the sentence, such as those that distinguish between restrictive and nonrestrictive elements in a sentence. But this comma that comes in to demarcate two independent clauses is entirely optional — in all contexts — if those two clauses are short and closely related. That’s a conservative move. Beyond that, in fiction, if you’re going for a particular voice, a particular effect, it’s perfectly permissible to omit this comma even with much longer structures. That’s deliberately and for effect though. You’ll see that approach more with some authors than others.
Example
The dragon’s head jolted off the ground and its lips curled away, revealing those sharp teeth.
“Set Free,” Andi Davis
Havok Online
Here, the two independent clauses within the structure are short and closely related. If they stood on their own, you might use the comma or not, depending upon the phrasing that was wanted. Do you want to emphasize these as two actions? Or cast them instead fluidly as one? If the first, use a comma. If the second, do not. The comma is entirely optional. Either way would be correct.
What follows these two clauses is not related, in the strictest sense, to both. It is a consequence of the second action, the lips curling away. But if you are painting the two clauses as one fluid action and then highlighting those sharp teeth, you’d punctuate as shown here. No comma to divide the clauses. Only the one comma to set off the participial phrase that flashes us the teeth.
Two Independent clauses both modified by the same dependent clause or introductory phrase
When an introductory phrase or clause, or any other dependent clause, equally modifies the compound structure of two independent clauses, the standard approach is not to use a comma.
This is yet another case where the overarching structure of the sentence governs decisions within it.
Example
Before I could react, something tugged at my feet and I lost balance, falling backward.
“Beware, Said the Man of Straw,” Jim Doran
Havok Online
Because the opening subordinate clause (“Before I could react”) applies to both of these short clauses that follow, it is best not to insert a comma between those two clauses. That is even more so the case because in this entire not-very-lengthy sentence, there are already two commas: one following the opening subordinate clause and one preceding the participial phrase. We definitely want those two commas. They are always called for. But to insert yet another comma here would be to lose any sort of shape this sentence now has. Now, I the reader can clearly see the shape, the opening piece, that closing piece. The two related actions in the middle (by virtue of not being separated by a comma) are grouped, as they should be.
Another consideration: were this middle portion to stand alone on its own as a sentence — “Something tugged at my feet and I lost my balance” — the comma between those short and related independent clauses would be optional.
So, all in all, omitting the comma here violates no conventions of punctuation and it assists meaning. Win-win.
Example
Stomach heaving in waves, my eyes water and the world becomes a flaxen blur.
“Lana’s Demon,” X. Culletto
Havok Online
Here, the contrast is between the opening phrase (“stomach heaving in waves”) and the remainder of the sentence, itself a compound (that is, two independent clauses). If this compound sentence were to stand on its own, without the opening phrase, you might well use the comma:
My eyes water, and the world becomes a flaxen blur.
That could work.
But subsumed into a larger structure, where these two actions are now to be understood as a unit, a unit in contrast to a separate condition — the heaving of her stomach — now, you would suppress that comma.
This is noncontroversial. There’s a lot of flexibility with commas having to do with compounding, the more so in fiction.
Compound subordinate clauses, misconstrued
Sometimes what appear to be two independent clauses are not. Instead, what you might think is a separate independent clause is in fact the second half of a compounded dependent clause.
The punctuation then (that is, not using a comma to divide that compound dependent clause) is completely conventional, but the structure may not at first be recognized for what it is.
Example
Only once did she refuse to try it, when I forgot to stir the noodles in the pot and they melded into one big lump.
“Lana’s Demon,” X. Culletto
Havok Online
Here, the main clause (“only once did she refuse to try it”) is being juxtaposed with the entirety of what follows (“when I forgot . . . and . . .”). If a comma were to be inserted here, dividing this subordinate clause into two pieces, we would lose that contrast.
In fact, if you were to diagram the entire subordinate clause on its own, you’d see that what might appear at first to be two clauses are both logically governed by the subordinating conjunction (“when”). In other words, it’s one subordinate structure:
when
I forgot to stir the noodles in the pot
and
they melded into one big lump
That’s not to say that, were this to stand on its own (as a fragment), you couldn’t add in that comma, if that’s the pacing you wanted. With commas of conjunction, there’s quite a bit of stylistic flexibility.
Example
That point was driven home when the bush erupted in flames and she had to once again dance out of the way.
“Set Free,” Andi Davis
Havok Online
Here, the main clause (“the point was driven home”) is again being juxtaposed with the entirety of what follows (“when the bush . . . and . . .”). The entirety of what follows is again one clause, a dependent clause, attached to the main clause. You would ordinarily not divide the two parts of a compound dependent clause: that clause is one unit.
Dependent clauses differ from independent clauses in that way: they are governed by a subordinating word.
The whole structure scans something like this:
The point was driven home
when
the bush erupted in flames
and
she had to once again dance out of the way
Whether or not there’s a comma before the dependent clause is irrelevant. That has only to do with whether the clause is restrictive (no comma) or nonrestrictive (comma). But with the comma, the compounded clause may be easier to grasp? Particularly if you’re not used to scanning sentences in this way.
Other groupings
The overarching principle is that a comma need not be used between two short and closely connected independent clauses, period. This is often even more so the case when that unit of two is interwoven in various ways with other structures.
Punctuation aligns with intent.
Example
But then we grew up, and Dad left and Mom went to work, and that’s when it started.
“Lana’s Demon,” X. Culletto
Havok Online
The intent here is to group the middle two independent clauses as a unit, juxtaposing them against (on the one hand) “but then we grew up” and (on the other) “and that’s when it started.”
Although this coordinating conjunction conjoins two independent clauses, they are short and closely related. And adding in the comma would change the shape of the larger structure.
Not a “grammar and syntax” comma
Now, there’s an important point to be made with respect to grammar and syntax. This comma (as is the case also with the comma that ordinarily is not used to split a compound predicate) has nothing to do with syntax. It’s pure convention. A useful convention, yes, but not an ironclad and necessary grammar-informed rule.
It’s for this reason that there’s fluidity of use with these two commas, most particularly in contexts where voice and tone and writing style hold sway. But you will see these choices sometimes in dry contexts as well.
By contrast, commas that do follow from the grammar of a sentence — such as those to distinguish restrictive from nonrestrictive elements — must not be tampered with.
Both of these stylistic choices — the typical comma between two independent clauses suppressed, the typically no comma to split a compound predicate added — are more common in fiction and narrative (that is, creative) nonfiction, whether literary or genre, and in anything written to be appreciated for the style of the telling as much as for the thoughts being conveyed.
They are less common in purely informational texts. When you find them used in these contexts, it will more often be for reasons of clarity.
The important point is: you’d not always, always leave out this comma. Do so only when that fusion buys you something, whether in terms of stylistics or clarity. When you do that, you’re using the flex that exists in punctuation to good purpose.