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Punctuating Style in CMOS 17: What’s New with Colons, Commas, Dashes, and Slashes

This article originally appeared in Copyediting newsletter, which explains the low word-to-humor ratio, and is reproduced with permission from the Pilcrow Group.

Since breaking news of the 17th edition, out in September, The University of Chicago Press has revealed some major revisions to The Chicago Manual of Style. Among the previews: lowercasing internet, dropping the hyphen in email, adding alt text to the manual for accessibility, improving keywords for searchability, expanding source citations to cover social media, and accepting themself to refer to a singular antecedent (as in they bought themself a book on quotations). Punctuation guidelines have also undergone a few tweaks, and though not nearly as controversial as going from e-mail to email, the following updates introduce new rules or clarify old ones for added finesse and flexibility.


  • When introducing a list or series, the words preceding the colon no longer need to be a grammatically complete sentence if the verb is understood: New: metadata, abstracts, and keywords.


  • Reword the sentence when the serial comma causes ambiguity. When the serial comma might be misread as framing an appositive, one solution is to repeat the conjunction: Instead of she drove her wife, the teacher, and her mother, use she drove her wife and the teacher and her mother.
  • Use a comma after “etc.,” “et al.,” and “and so forth” only if required by the surrounding text. Instead of setting these terms off with a pair of commas according to the previous recommendation, treat them as equivalent to the final element in a series: The editor donated a dozen outdated reference books (without removing dog-ears, pencil marks, sticky notes, etc. from the pages).
  • Capitalize the first word of a direct question not enclosed in quotation marks when it follows a comma. Another departure from previous editions, this guideline makes this category of question analogous to a direct quotation: He wondered, Should I track changes?
  • It’s not necessary to precede the adverbs “too” and “either” with a comma when used in the sense of “also” at the end of a sentence. They couldn’t make the deadline either. The printer was down too.
  • In correspondence, a greeting containing a direct address requires two punctuations: a comma in the direct address and a colon or comma after the greeting.

Welcome, readers: . . .
Hi, Laura, . . .

But in casual correspondence, the direct-address comma is often omitted.

Hi Erin, . . .

Em Dashes

  • In printed publications, break the line after an em dash, not before. But when another punctuation mark immediately follows the dash, like in this example, keep the elements together:

“I’m saving my edits before I—”
the student said as the computer froze.

En Dashes

  • In printed publications, break the line after an en dash, not before. But if it pushes a single character to the next line, such as part of a number range or a score, keep the elements together.
  • An en dash with a space before and after may be used instead of an em dash in running text. Primarily a British style, an en dash as em dash is preferred by many U.S. publishers and writers.


  • In printed publications, break the line after a slash, not before. But if it pushes a single character to the next line (such as when it is part of a two-year span) or splits a fraction, keep the elements together. This new rule doesn’t apply to poetry line breaks (break before or after) or URLs (break before).

Multiple Punctuation Marks

  • Except in formal prose, a question mark can be combined with an exclamation point to “express excitement or disbelief.” Are we another step closer to adopting the interrobang?!

Visit CMOS Shop Talk for Chicago style–related news, advice, and quizzes.


Slashes: Uses and Restrictions

Misunderstood. Abused. Ignored.

No, not me. Well, maybe that, too, but I’m referring to the beleaguered slash, which you may know as a diagonal, virgule, solidus, slant, stroke, oblique stroke, separatrix, shilling mark, or forward slash (that low-self-esteem retronym which seeks to distinguish the slash [/] from the backslash [\]).

With this many names and almost as many roles—like providing alternatives, adding, abbreviating, separating, joining—the slash is like the understudy who also prints the flyers and strikes the set with the stagehands. Even so, The Associated Press Stylebook chose to exclude the slash from the “Punctuation” section, acknowledging it with a thirty-word chin nod in the main section instead. (It could be worse: The en dash was completely forsaken.)

[In AP style,] slashes are acceptable only in certain phrases and “special situations,” such as with fractions.

It may surprise you to learn that the most common usage of the slash, as a signifier of alternatives/options/choices, has been barred in AP style; slashes are acceptable only in certain phrases and “special situations,” such as with fractions. A heavy user of slashes and other intoxicating punctuation such as semicolons, I do admit to relying upon them to organize the contents of my brain when I’m in a hurry. And why not? They’re free, and I can use the time I’m saving for more important tasks, like chewing properly.

Slashes: Differences Between AP and Chicago Style

AP: We never said that slashes are tacky or that using them is lazy, but we’re cool with those inferences. Here are the acceptable uses.

  • With fractions
  • Between lines of quoted poetry
  • In Internet addresses (URLs) and pathnames
  • In descriptive phrases such as 24/7 or 9/11
  • In the signoff (credit) in photo captions

AP doesn’t explain this, but in the stylebook, the slash is also used in abbreviations such as TCP/IP and NAA/IPTC.

In the 14th edition (1993) of The Chicago Manual of Style, the slash was listed under “solidus” and was summed up in one paragraph. Cute, right? It didn’t make the first edition, in 1906, but that was a two-hundred-page baby compared to today’s thousand-page sumo wrestler.

Chicago: We love our versatile little friend. Here are some of its uses.

  • With fractions
  • Between lines of quoted poetry
  • In Internet addresses (URLs) and pathnames
  • To signify or or and/or
  • With two-year spans, e.g., 1991/92 (instead of an en dash)
  • With dates (informal), e.g., 6/1/11
  • In abbreviations, e.g., $7/hour (instead of per) and c/o (instead of a period)

So that’s the nitty-gritty of slashes and style.

When in doubt, ditch the spaces and you’ll be right most of the time.

Now, let’s talk about how to render a slash in certain contexts to improve readability, which is, after all, the heart of copyediting. (Or the lungs. Some vital organ.) Non-editors tend to either compulsively add spaces around all slashes or close them all up. When in doubt, ditch the spaces and you’ll be right most of the time; however, Chicago has an option for handling open compounds (two or more words separated by a space, e.g., copy editor) that offers more flexibility and clarity—totally worth memorizing. More on that coming up.

General Rule for Using Spaces With Slashes

In most cases, there are no spaces on either side of the slash. This is especially true for unique (read: inflexible) constructions such as directory paths and filenames, where our use of the slash is driven by requirement, not style.

Brief rant: There’s a rogue slash style making the rounds, usually on résumés, for some reason: no space before the slash but one after. I’m not impressed by this. It’s a red flag that points to poor decision-making more than anything else; even if executed consistently, it isn’t a style which showcases a copy editor’s skills. Rather, it may expose them as a street editor (as in any schmoe off the street). Not that I don’t appreciate this heads-up.

Exception: Quoted Poetry

AP: To show line breaks when quoting poetry in running text, use a slash between the lines, with a space before and after the slashes.

Chicago: Ditto. And when quoting more than one stanza in running text, insert two slashes [//] between the stanzas.

Although Chicago discusses this explicitly, AP actually doesn’t say anything about putting spaces around slashes for quoting poetry—only that slashes can be used to denote “the ends of a line in quoted poetry.” Good enough for me!

Exception: Open Compounds

Chicago: If one or both of the terms separated by the slash consist of two or more words, a space before and after the slash may aid comprehension.

This option really appeals to me, because it helps to visually group an open compound, making it clear that words beyond the ones immediately surrounding the slash are part of the thoughts being weighed.

The 15th edition had prescribed a thin space before and after; in the 16th edition, we’ve graduated to a full space, certainly a more realistic option for writers, editors, and typesetters. (Spacing slashes was not even addressed in the 14th edition.) I applaud this move towards simplicity and am looking forward to a thinner edition in CMOS’ next incarnation. Well, I can dream, at least.

I applaud this move towards simplicity and am looking forward to a thinner edition in CMOS’ next incarnation.


  • AP, 2011: “slash” and “Internet”; “Photo Captions” section
  • CMOS, 16th edition: slashes, 6.103-110; periods with abbreviations, 10.4; running in more than one stanza of poetry, 13.32