Q. Is it okay for “%” to be changed to “percent” in quoted text to match the rest of the document, similar to how you can change en dashes to em dashes in CMOS 12.7?

A. It’s better to leave the symbol as is. Readers who look for the original text of a quotation that includes “a 7 percent increase” may have trouble finding the relevant passage if it has “a 7% increase” instead—or, if not, they may wonder what other changes have been made without notice.

By comparison, dashes are dashes. A reader consulting the source of a quotation that included “a 7 percent increase—defying all expectations” is unlikely to be tripped up by finding “a 7 percent increase – defying all expectations.”

In other words, we consider the difference between dashes to be purely typographical, whereas the difference between “%” and “percent” is just beyond that threshold—more like a case of synonyms.

Q. In the following sentence, is it correct to use an en dash after 25 but a hyphen after 30? “The report referred to a 25– to 30-year-old oak tree on the perimeter of the parking lot.”

A. It looks as if you’re trying to extend the logic behind expressions like “pre–Civil War,” where the idea is that an en dash, which is longer than a hyphen, bridges the space in “Civil War” to apply the prefix “pre” to both words in that phrase.

But Chicago style for your example would be to write “a 25-to-30-year-old oak tree,” with four hyphens. Only in the case of two different ages rather than a range would we recommend something like what you’ve written, but with a suspended hyphen instead of an en dash: “a 25- or 30-year-old oak tree”—which is short for “a 25-year-old or 30-year-old oak tree.” (See CMOS 7.96, section 1, under “age terms.”)

In each of those examples, the hyphen in “25-” is like the one in “30-”; an en dash rather than a hyphen after the first number might look like a mistake, and it wouldn’t necessarily make the expression any clearer. For more on suspended hyphens, see CMOS 7.95.

Q. Is it incorrect to include a space before a question or exclamation mark? E.g., “Do you like chocolate ?” Thank you.

A. In English? Yes, a space would be incorrect. But if you’re writing for a French audience, such a space would be expected. Just make sure it’s a nonbreaking space (see CMOS 6.129).

If you set your proofing language to French (under Review > Language), Microsoft Word will add a nonbreaking space next to certain marks of punctuation automatically as you type—not only before question marks and exclamation points but before colons and semicolons and between French quotation marks (or guillemets, « ») and the text they enclose. Word includes more than a dozen varieties of French, from Belgian French to Swiss French, and most add these spaces; the setting for Canadian French adds them only for colons and guillemets.

In English, however, such spaces are not required even if you’re quoting a French source verbatim in an otherwise English-language document. For more details, see CMOS 11.31.

Did you know? French typesetters used to add spaces before commas also (but not periods). See “One Space or Two” at CMOS Shop Talk (esp. footnote †).

Q. How would you style Napoleon’s name in something like “They researched the tin buttons on the uniforms of soldiers in Napoleon’s army.” Merriam-Webster has “Napoléon I” under the “Bonaparte” entry but “Napoleon I” under the “napoleon” entry. Encyclopaedia Britannica has “Napoleon I” as its first entry. CMOS 5.128 has “if Napoleon was in fact poisoned” as an example. So should my example sentence have an accent on “Napoleon,” include the “I,” or include “Bonaparte”?

A. Although fidelity to a person’s name is an important consideration, Napoleon Bonaparte entered the English vernacular long ago—without the accent. So, whereas “Napoléon” is the correct spelling of that name in French (where the accent is mandatory), there’s no need to use the French spelling in an English-language context.

As for the Roman numeral, add it only when needed for clarity—for example, to distinguish Napoleon I (or, in French, Napoléon Iᵉʳ) from Napoleons II and III. (Superscripts like the one in “Napoléon Iᵉʳ” are generally retained in an English-language context; see CMOS 11.30.)

As for “Bonaparte,” you can usually add that at your first mention of Napoleon, who is otherwise typically referred to by his first name.

Q. Dear Manuscript Editing Department, I am proofreading a bibliography using CMOS and wanted to ask where the period should go relative to the following title of a journal article: “In/Visibility and the (Post-Soviet) ‘Queer Closet.’ ” That placement seems to be the generally accepted solution in American English. I wonder, however, if, for the computational age, the following solution were not more appropriate: “In/Visibility and the (Post-Soviet) ‘Queer Closet’.” I find that it makes the string that one copies in order to search for it online correspond to what is in databases and on journal sites. Many thanks!

A. The period does look good between the two marks—where it solves the spacing problem between consecutive single and double quotation marks (we’ve added a narrow nonbreaking space to the first version of the title in your question, per CMOS 6.11)—but it’s not Chicago style.

And though we could make an exception for titles like the one you cite, we’d arguably then need to apply that same exception for periods (and commas) relative to single quotation marks everywhere for the sake of consistency—which, again, wouldn’t be Chicago style.

As for searches, the placement of the period (as well as its presence or absence) didn’t seem to make any difference in our tests, whereas the quotation marks and other marks of punctuation in the article title caused the occasional hiccup in certain library databases.

For a brief history of quotation marks relative to periods and commas—including the rationale for Chicago style (and, by extension, American English style)—see “Commas and Periods with Quotation Marks” at CMOS Shop Talk.

Q. I find ISBNs extremely useful when trying to locate copies of books of interest, especially when searching for secondhand copies of out-of-print books, for requesting books on interlibrary loan, and for disambiguating common names or titles. I’m writing a literature review in the form of an annotated bibliography and would like to include ISBNs in the entries for those books that have them, as a convenience and finding aid for readers. I can’t find any guidance for inclusion of ISBNs in Chicago-style footnotes or bibliography entries, even as an optional item. Can you provide a recommended template or example of placement and formatting?

A. Sure. Here’s how we’d recommend adding ISBNs to the bibliography entries for three different editions of Daniel James Brown’s bestselling book about a rowing team’s quest for Olympic gold at the 1936 Berlin Olympics (listed here in chronological order, from the 2013 Viking hardcover to the 2023 Penguin Books movie tie-in edition):

Brown, Daniel James. The Boys in the Boat. Viking, 2013. ISBN 978-0-670-02581-7.

Brown, Daniel James. The Boys in the Boat. Penguin Books, 2014. ISBN 978-0-143-12547-1.

Brown, Daniel James. The Boys in the Boat. Movie tie-in ed. Penguin Books, 2023. ISBN 978-0-593-51230-2.

In general, an ISBN or other optional information may be added to an entry in a bibliography when needed, following the period at the end of the other citation data. But if you need to include an ISBN within a note, we’d suggest adding it in parentheses, as part of the facts of publication:

1. Daniel James Brown, The Boys in the Boat, movie tie-in ed. (Penguin Books, 2023; ISBN 978-0-593-51230-2), 33–34.

The hyphens in the ISBN, which are optional, will help those who need to manually copy or type the number. For more on ISBNs and how they work, start with CMOS 1.36 and these FAQs from ISBN.org.

Q. Hello, Chicago doesn’t seem to have an example of how to cite a contribution to a new edition of a book. Should the edition number follow a period or comma in the reference list entry below? Though my example is in Chicago 17 style, the question is still relevant for Chicago 18 style, so I would appreciate your guidance. Thanks!

Rothbard, Murray N. 2006. “The Libertarian Heritage: The American Revolution and Classical Liberalism.” In For a New Liberty: The Libertarian Manifesto, 1–23. 2nd ed. Auburn, AL: Ludwig von Mises Institute.

A. The best place for an edition number for a book is usually just after the title. When it’s part of an “In . .  .” statement (as in your example), it follows a comma. As of the 18th edition, Chicago no longer requires a page range for a chapter or other contribution to a book or a place of publication, so your author-date entry would look like this:

Rothbard, Murray N. 2006. “The Libertarian Heritage: The American Revolution and Classical Liberalism.” In For a New Liberty: The Libertarian Manifesto, 2nd ed. Ludwig von Mises Institute.

(If you were following CMOS 17, the edition number would precede the page range: “. . . Manifesto, 2nd ed., 1–23. . . .”) In a reference list entry for the book as a whole, the edition number would follow a period:

Rothbard, Murray N. 2006. For a New Liberty: The Libertarian Manifesto. 2nd ed. Ludwig von Mises Institute.

Bibliography entries would follow the same pattern (except for the placement of the year of publication; see CMOS 14.1).

Q. In the word-by-word alphabetizing example in CMOS 15.69, why are “New, Zoe” and “News, Networks, and the Arts” before “New Deal” and “news conference,” respectively? Thanks.

A. As explained there, in the text introducing a comparison of the two basic systems of alphabetization—letter by letter and word by word—a comma “interrupts” alphabetizing in both systems. This means that any words that follow a comma are ignored unless what comes before the comma is identical in two or more entries:

New, Arthur [alphabetized under “New”]

New, Zoe [also alphabetized under “New”; “Zoe” follows “Arthur”]

New Deal [alphabetized under “New Deal” (which follows “New”)]

news, lamentable [alphabetized under “news”]

News, Networks, and the Arts [also alphabetized under “News”; “Networks” follows “lamentable”]

news conference [alphabetized under “news conference” (which follows “news”)]

The order of the terms above would be the same in the letter-by-letter system. But in letter-by-letter order, a space between words is ignored. So, for example, “newborn” would come before the phrase “New Deal” in the letter-by-letter system (because “newb” comes before “New D”), whereas the opposite would be true in a list arranged word by word, in which alphabetizing stops after the first word in each entry (the word “New” comes before “newborn”). Note that Chicago now prefers the word-by-word system (as of the 18th edition; see CMOS 15.66).

Q. Why is ibid. preferable to id.? The meaning is essentially the same and id. is more succinct, and it is used extensively in legal citation without any apparent confusion or misunderstanding.

A. What you say is true. But because id. (idem, the same) is used mainly in legal citations whereas ibid. (ibidem, in the same place) has long been preferred in history and most other academic disciplines, ibid. is much more well known than id. Whether ibid. also benefits from not looking like id (the complement to the ego and superego) is anyone’s guess.

For more on ibid. and id. (including Chicago’s preference for shortened citations over either of those abbreviations), start with CMOS 13.38.

Q. When writing technical documentation, some steps may require a warning or information of note with the step. In those instances, the information begins either with “Warning:” or “Note:” (respectively). If the word before the colon is bolded, should the colon also be bolded?

A. In the scenario you describe, the colon belongs to the word it’s next to rather than to the words that follow. If the former is in a bold font—or in italics or a different color—then the colon would be styled to match:

Warning: Don’t press this button.

Note: Some buttons are more important than others.

See CMOS 6.2 and 6.3 for some additional considerations and examples.

Q. Hello! You have a Q&A where a speaker interrupts their own dialogue with an em dash, and your example uses a space before the new sentence: “I thought I might— Oh, it’s no use.” While I understand the logic of the space (the first sentence has ended suddenly; a new one starts), in practice, is there a justification for just closing up the spaces with all such em dashes for expediency and consistency, even if what follows is a complete sentence? Our global manuscript cleanup process would remove that space even if the author had written it in, and I am reluctant to have copyeditors spend time adding the space back in on a case-by-case basis, agonizing over whether the next clause merits a space and a cap (if it’s ambiguous), and so on. Is there room for a house style exception on this, or do you think that the space should be followed as a matter of Chicago style? Thank you for any help!

A. That space after the em dash in “might—” isn’t technically Chicago style; it’s not currently covered in CMOS itself (as of the 18th edition). But as our Q&A implies, we do think the space (followed by an initial capital) is useful—as does Benjamin Dreyer, the author of Dreyer’s English (Random House, 2019; see p. 124).

Still, it’s a small detail that isn’t likely to be missed if it’s not there in the first place. But if you do make an executive decision to clean out spaces after em dashes, consider changing the initial capitals that follow them to lowercase (except in proper nouns or initialisms or the like); absent that space, a capital may look to some readers like a mistake (though maybe less so in styles that put a space before and after a dash):

“I thought I might— Oh, it’s no use.”

becomes

“I thought I might—oh, it’s no use.”

not

“I thought I might—Oh, it’s no use.”

The first example is arguably best; it conveys the self-interruption more definitively than the others do. But if your editing resources are limited, this is one detail that, again, could be left on the cutting-room floor. Just be sure to alert your authors to what you’ve done when you return their copyedited manuscripts for review; they should get a chance to restore any spaces plus initial capitals that they think are mandatory.

Q. Should the indefinite article “a” be used when introducing a professor emeritus? For example, “He is [a] professor emeritus of chemistry at the university.” On the one hand, “a” usually indicates that the person is not the only person with that title at the university. On the other hand, Google Ngram shows a higher preference for no article.

A. We agree that adding “a” could make sense if there’s more than one such professor at the university in question. But whether there’s one or eleven, omitting the article makes “professor emeritus” sound more like a professional title than a job description. That is, it sounds fancier.

This may explain why it would be relatively rare to refer to someone as “teacher of” chemistry or another subject (without “a”), whereas calling someone “professor of”—even without “emeritus”—is fairly common (“She is professor of chemistry at . . .”). The word professor enjoys a status that teacher does not.

In other words, there’s no definitive answer to your question. Though adding an “a” or an “an” can work well before a title held by more than one person, omitting the article before “professor” and variations of that term even when there’s more than one can be an equally good choice, one that follows an unstated convention in academia.

Q. The 18th edition says to include “The” when part of an official periodical title. What about upper- or lowercasing “The” in organizations such as The Juilliard School or The Metropolitan Museum of Art? (I prefer lowercase, but they refer to themselves with “The.”)

A. Chicago’s new guidelines relative to an initial article in names like The New York Times do not extend to the names of organizations. The main reason behind this difference is that the names of organizations aren’t set off from the surrounding text by italics or quotation marks.

The occasional exception can be made on a case-by-case basis—like the exceptions made by Julliard and the Met when writing about themselves (or by the University of Chicago Press in its copyright lines, including at the foot of this page: “© 2024 by The University of Chicago”). But when you refer to organizations other than your own, there’s generally no obligation to capitalize an initial “the.”

Q. How would you cite a website home page in a bibliography? Would the page title be “Home Page” (in quotes) or just a descriptive “Home page” (no quotes)? Or the title of the website? Or something else entirely?

A. A home page is almost never titled “Home Page,” so a description is your best option (though you can leave that out if it’s obvious from the URL and the other information in your citation). Note also that a home page isn’t normally a source that you’d list in a bibliography; consider limiting your citation to a mention in either the text or a note (though we’ll show the form for a bibliography entry here).

Wherever you cite it, you should save a version of the page as it existed when you consulted it. Unlike a published article or other content that may be available from a home page, a home page itself is designed to change over time (i.e., as a site adds content or to keep up with new software, or both).

If it is important to share this version with your readers, use the Internet Archive’s Wayback Machine or a similar service to create a public link and cite that version as follows:

University of Chicago Press (home page). Archived November 27, 2024. https://​web​.archive​.org​/web​/20241127140410​/https://​press​.uchicago​.edu​/index​.html.

That’s the page at https://press.uchicago.edu/index.html as it existed on November 27 at four minutes and ten seconds after two in the afternoon UTC (the string of numbers in the middle of the URL; that link points to the page as saved using the Wayback Machine’s Save Page Now feature). If you do not cite an archived version, you will need to include an access date. For more details and examples, see CMOS 14.104. For the meaning of UTC (Coordinated Universal Time), see 10.47.