Q. “He wanted to see his friend John Smith before going out”? Or “He wanted to see his friend, John Smith, before going out”? I know the rule for spouses and siblings (as in CMOS 6.31), but what about friends?
A. Because people usually have more than one friend, the first version, the one without commas, will almost always be correct. Even those who might claim to have just one friend could make another one at any time. Besides, friend is an elastic concept that can apply to people who aren’t exactly “friends.”
All this to say that, without additional context, the word friend by itself isn’t enough to tell us who you’re talking about in an example like yours (Which friend?), so the name (John Smith) is essential (or restrictive) and shouldn’t be set off by commas.
By contrast, people generally have only one spouse at a time, making commas the default when a name follows a word like husband or wife: “She wanted to see her husband, John Smith, before going out.” In that sentence, the word husband alone narrows things down to one person; the name gives extra information that isn’t essential (it’s nonrestrictive) and is thus set off by commas. (They’re called spousal commas and not friendship commas for a reason.)
For more on commas like these (and why even spousal commas can be omitted sometimes), see “Your Dog[,] Smurf: Understanding Commas with Appositives,” at CMOS Shop Talk.
[This answer relies on the 18th edition of CMOS (2024) unless otherwise noted.]
Q. I haven’t been able to find anything in CMOS about how to punctuate a sentence that begins with a dependent clause that consists of two independent clauses introduced by a word like “If.” I’m a proofreader for court reporters. One of my clients consistently puts a comma within this type of dependent clause, but I don’t think the comma should be there. The comma I’m asking about is the comma after the word “valve” in the following example: “If you had to replace a leaking valve, and it had external insulation, how long would that work take?” To me, the part about external insulation is restrictive and should not be preceded by a comma. I’d like to find some authoritative confirmation of that. Thank you.
A. We agree that the first comma in your example is best omitted, not because the clause following and is restrictive (and doesn’t normally work that way) but because that comma competes with the one that is normally required after an if clause. So:
If you had to replace a leaking valve, how long would that work take? (The comma is required; see CMOS 6.26.)
If you had to replace a leaking valve and it had external insulation, how long would that work take? (A comma after “valve” would be strictly correct but is usually best omitted.)
To make a long story short, omitting the comma after valve from your example makes it clearer that the introductory If applies to both clauses (i.e., “you had . . .” and “it had . . .”). For a similar take, see this previous Q&A (which refers to the 17th ed. but still applies).
To understand how all this works, it might also help to consider your example sentence with that instead of and (though in your situation any changes to wording presumably wouldn’t be an option):
If you had to replace a leaking valve that had external insulation, how long would that work take?
In that case, that introduces a restrictive relative clause (see CMOS 6.29). And though it doesn’t change the meaning of your example, the word that can help ensure a restrictive reading of the “insulation” clause.
We’ll try to clarify these options in a future edition of CMOS.
[This answer relies on the 18th edition of CMOS (2024) unless otherwise noted.]
Q. Hello, Chicago. Thanks for your time. I’d like you to confirm the optional comma after a one-word adverb of time (tonight, yesterday, today) starting a sentence. One of my fiction authors is upset because Word is showing blue lines under those words. I told her a comma is optional and Word doesn’t get the nuances. Would you please confirm this so I can calm my jittery author? Thanks again.
A. It can be hard to ignore Microsoft Word’s blue underlines, especially when they’re worded in a way that suggests you’d be wrong to keep the text as is: “After an introductory word or phrase, a comma is best.”
But you can tell your author that we agree with you. In the words of CMOS 6.34, “Although an introductory adverbial phrase can usually be followed by a comma, it need not be unless misreading is likely. Shorter adverbial phrases are less likely to merit a comma than longer ones.”
The adverbs yesterday, tonight, and today aren’t phrases, but each of them derives from one (yesterday comes from Old English giestran dæg), and it’s clear that each is grammatically equivalent to a phrase like next week or in 1965. Plus, any one of these words would qualify as short in the context of introductory adverbial phrases.
To be fair to Word, tonight is the only one among the words and phrases mentioned above (from yesterday through in 1965) that Word’s grammar checker flagged in our tests when it wasn’t followed by a comma (as of July 1, 2025). Conversely, Word didn’t stop on any of them when they were followed by a comma. So it’s not that far out of line with CMOS.
Tip: To avoid falling under the influence of Word’s blue underlines, some writers prefer to toggle them off as they draft. A convenient way of doing this is to add a button to the ribbon. In Word for Windows (the desktop version), go to File > Options > Customize Ribbon. Then select All Commands under “Choose commands from” and scroll down until you find Hide Grammar Errors. You can then add that command to a new group under the Home tab (or wherever you want it to appear). Steps for Word for Mac will be similar.
If you use the option under Customize Ribbon to assign a keyboard shortcut to the equivalent command (look for ToolsGrammarHide under the All Commands category in the separate dialog box for keyboard shortcuts), keep the button, which has the important advantage of showing whether it’s on or off (via shading/outline).
[This answer relies on the 18th edition of CMOS (2024) unless otherwise noted.]
Q. With coordinate adjectives separated by a conjunction, there’s no comma: “A stable and sensible approach.” I assume it would be the same for contrasting adjectives: “A sensible yet volatile approach.” Though if you wanted to emphasize the volatility, you might set it off with commas: “A sensible, yet volatile, approach.” Does this all sound right?
A. That sounds right to us, though whenever you interrupt an adjective-plus-noun construction with an intervening phrase set off by commas, the result tends to be a little awkward. If you want to smooth things out while keeping the emphasis on volatility, try rephrasing. For example:
an approach that’s sensible yet also volatile
a sensible approach, albeit a volatile one
Or you could embrace the interruption by applying something stronger than commas:
a sensible—yet volatile—approach
a sensible (yet volatile) approach
See also CMOS 6.51.
[This answer relies on the 18th edition of CMOS (2024) unless otherwise noted.]
Q. In text, I write: “. . . a book titled, ABC Book.” But should I use the word “titled” or “entitled” in front of the title? Also, should the title be preceded by a comma, as I’ve done here? I’ve always included the comma, but that may not be correct. Please help. Thanks!
A. Both titled and entitled are correct, and in this context they mean the same thing. Normally, you can use titled—that is, unless you’re feeling entitled (the other meaning of that word) to use the slightly fancier-sounding entitled.
But omit the comma before the book title. Many writers assume that a comma is needed before the title of any book or other work mentioned mid-sentence, probably because the words in italics or quotation marks resemble quoted writing or speech. In other words, titled (or entitled) is often treated (incorrectly) like said would be.
Instead, you should save your commas for direct quotations introduced like the one in the third example below (but not the fourth one; see also CMOS 12.14):
I just started writing a book titled ABC Book.
and
The first chapter is called “It’s Now or Never.”
but
My publisher said, “It’s now or never.”
or
My publisher said that “it’s now or never.”
[This answer relies on the 18th edition of CMOS (2024) unless otherwise noted.]
Q. Would you use a comma between two independent clauses that are both subordinate to the same “if”? For example, “The qualifying relative would have suffered if the waiver had been denied[,] and the applicant had not been present to help her through her cancer treatments.” I’m looking in CMOS 6.26, but the advice there doesn’t exactly match this situation. Could you please assist?
A. Good question! Though retaining the comma in an example like yours wouldn’t be strictly wrong, omitting it will help readers understand that both clauses following the subordinating conjunction if (“the waiver . . .” and “the applicant . . .”) depend on that same word. This logic would continue to hold if you were to invert the sentence (though a comma would then be required after the second if-dependent clause): “If the waiver had been denied and the applicant had not been present to help her through her cancer treatments, the qualifying relative would have suffered.”
See also CMOS 6.24 (commas with introductory dependent clauses) and 6.25 (commas with dependent clauses following the main clause).
[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]
Q. I recently wrote a book where some headings listed tasks and challenges. For example, “Task 1, Learn as Much as You Can about the Disease” and “Challenge 1, Adopt a New Attitude.” Someone told me the punctuation was wrong and the commas should have been colons. I think that either commas or colons are correct. Am I right?
A. You are right—either mark is correct, but a colon isn’t the only alternative to a comma:
Task 1: Learn as Much as You Can . . .
Task 1. Learn as Much as You Can . . .
Task 1—Learn as Much as You Can . . .
Task 1, Learn as Much as You Can . . .
Those examples are listed in descending order of effectiveness. A comma would be most appropriate as sentence punctuation (and we’re styling task numbers like page numbers here; see CMOS 9.26):
Now let’s turn to task 1, “Learn as Much as You Can . . .”
In a heading or a list, either a colon, a period, or a dash—each of which creates a stronger break than a comma—would work a little better at making it clear that “Task 1” is an enumerator and not part of the enumerated item. So you’re not wrong, but your challenger isn’t entirely wrong either.
[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]
Q. I can’t get a definite answer on how to punctuate a sentence that starts with “trust me.” For example, “Trust me, you don’t want to do that.” Would this be considered a comma splice? Would it be better to use a period or em dash, or is the comma okay? What about “believe me” or “I swear”?
A. Any phrase like “trust me” at the beginning of a sentence that is roughly equivalent to a “yes” or a “no” can normally be followed by a comma (as covered in CMOS 6.34):
No, you don’t want to do that.
is like
Trust me, you don’t want to do that.
whereas
Yes, I’ve edited the whole document.
is like
Believe me, I’ve edited the whole document.
and
I swear, I’ve edited the whole document.
You could use a stronger mark of punctuation for extra emphasis:
I swear! It’s not a comma splice!
or
I swear—it’s not a comma splice.
among other possibilities
But a simple comma will be the best choice in most contexts (and won’t get you in trouble for using a comma splice—at least not with us).
[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]
Q. If you’re replying to someone and want to say thank you, would you write “Thank you John” or “Thank you, John”?
A. If you happen to know that the object of your gratitude is a stickler for vocative commas, then write “Thank you, John.” Otherwise (and unless the context is formal), feel free to leave the comma out, a choice that suggests a certain degree of spontaneity and a friendly disregard for the rules. But if you’re an editor of any kind, use the comma regardless of what anyone might think; you have your reputation to maintain. For more on these commas, see CMOS 6.53.
[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]
Q. I’m having a difficult time finding a rule that governs afterthoughts. For example: “I told him I would pay my respects another time, if necessary.” Comma before “if”? Seems like there should be.
A. Anything intended as an afterthought should be preceded by a comma, or by some other mark of punctuation—a dash, for example (or parentheses). A period could also work. In your example, the comma before “if” is the only thing that tells readers that “if necessary” is an afterthought. So keep it, assuming that’s what you intended.
[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]