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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to the previous recommendation, treat them as equivalent to the final element in a series: The editor donated a dozen outdated reference books (without removing dog-ears, pencil marks, sticky notes, etc.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?!

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