The rules in The Chicago Manual of Style have never been carved in stone, as the preface to the first edition reminds us. Not only are they to be applied “with a certain degree of elasticity,” but they are subject to periodic revision as publishing practices and cultural expectations evolve. For this edition of the Manual, its eighteenth, our editors have once again reconsidered the rules and recommendations established in previous editions and, with input from a team of advisers and many others both inside and outside the University of Chicago Press, updated them to meet the needs of a new era. Readers everywhere have come to expect instant access to documents from practically every period of recorded history, in a nearly endless variety of styles and genres, and “Chicago style” needs to make sense within this larger context. This edition, the most extensive revision in a generation, balances tried-and-true editorial logic with an attention to real-world usage based on evidence that is easier than ever to find and evaluate.
The challenges inherent in maintaining this balance can be illustrated with a story from the Manual’s history. The words Roman and Arabic have long been capitalized in the context of numerals, as they were in the first eleven editions of this manual (starting in 1906, long before Chicago was added to its title). But then the editors of the twelfth edition (published in 1969) decided to impose lowercase: Not only had Roman and Arabic numerals lost much of their literal association with the long-ago cultures from which they came, but lowercase would align with the similar pairing of roman and italic in the context of type (italic is related to the proper adjective Italian), where it was already the norm. This change, however, failed to catch on, as anyone can now discover from the latest dictionaries and other online sources, including searchable corpora that track how words and phrases have been used over time (even with respect to capitalization) in books and other documents. For this edition we have therefore reversed course, a rare but necessary concession to actual usage.
More significant is our support for capitalizing words like Black, White, and Indigenous when they refer to people (see chapter 8). Though such adjectives are not derived from proper nouns (a consideration that would normally argue for lowercase), and though some writers will prefer lowercase, capitalization adds a semantically useful distinction between these terms and their generic lowercase counterparts, one that is increasingly recognized by dictionaries and other authorities. We now also endorse the use of singular they as needed to refer not only to someone who is nonbinary but also to anyone whose gender is unknown or irrelevant (or concealed for reasons of privacy), a natural development in a language that lacks a dedicated gender-neutral pronoun for people—and one that increasingly reflects real-world usage. Chapter 5, in addition to covering singular they from the standpoints of both usage and grammar, now includes discussions of person-first versus identity-first language and related concepts in a thoroughly revised section on inclusive language developed with the oversight of our advisory board and other key reviewers.
This edition also adds some significant new content, including sections on Indigenous languages and sources (in chapters 11 and 14, respectively), which benefited from the input of reviewers who are experts in these subject areas. We also received expert oversight for the new material on Korean language and romanization (in chapter 11), which complements our existing coverage of Chinese and Japanese. This new content, like many of the updates and refinements in this edition, grew out of questions and suggestions from readers writing to us via our Q&A.
Our readers also asked for more coverage of fiction and other creative genres, though not always directly: The many questions sent to us over the years from writers and editors whose focus is more literary than academic have made it clear that these genres are important to our readers and that our coverage is long overdue. The new material (some of which was developed at CMOS Shop Talk, our blog in support of the Manual) can be found in chapter 12 (in new sections on formatting and punctuating dialogue), as well as in our expanded recommendations on the parts of a book in chapter 1 and punctuation in chapter 6. Fiction and related genres also play a role in chapter 11, where we discuss the use of italics in multilingual narratives and dialogue. These and other sections throughout the Manual have also been updated to consider the needs of independent authors who self-publish their work (and the editors and others who collaborate with them).
In response to evolving standards for content published in digital formats, we have expanded our coverage of accessibility. In addition to providing advice on writing alternative text (or “alt text”) for images in chapter 3, we now include key terms related to accessibility in a revised and expanded glossary and a new section devoted to accessibility in our bibliography. In chapter 2, we discuss strategies for checking accessibility in ebooks and other electronic formats to ensure conformance with applicable standards. And in CMOS Online, we now present our numbered tables as accessible HTML-formatted text.
The chapters on source citation, a pillar of Chicago style, have been reorganized with both new and experienced researchers in mind. A detailed and thorough overview of our two systems of citation—notes and bibliography (our primary system) and the stylistically similar author-date—is the subject of chapter 13. This is followed in chapter 14 by examples organized by type of source, from books and journal articles to legal and public documents. And rather than continuing to relegate author-date examples to a separate chapter as in previous editions, we now present them alongside the examples in chapter 14 for sources that might be difficult to cite in author-date format based on examples of notes and bibliography entries alone.
We have also reconsidered our coverage of math. Though we wanted to retain our math-related content in some form, usage data from CMOS Online for the chapter dedicated to this subject (and the lack of questions about it directed to us over the years) suggested that this specialized content was rarely consulted by our readers. We therefore eliminated the chapter and instead cover mathematical variables and other key concepts in chapters 3, 6, 7, 9, 10, and 12, where we hope they will be more useful to general editors.
Other changes are intended to clarify existing terminology and to bring Chicago style up to date with current practices. For example, we now refer to title case and sentence case rather than headline style and sentence style. Not only are actual news headlines often capitalized like sentences, putting the term headline style at odds with its intended meaning, but the word case (from upper- and lowercase) is more usefully specific in this context than style. On the subject of title case, we now recommend capitalizing prepositions of more than four letters in the title of a work (A Room with a View but Much Ado About Nothing). It is increasingly rare to find longer prepositions lowercased in titles, and this change aligns Chicago more closely with contemporary usage. In another title-related update, we now advise capitalizing and italicizing an initial The in the title of a periodical that includes one (as in The New Yorker), making such titles more consistent with other types of italicized titles (though we still support dropping the initial article from periodical titles in source citations and index entries).
As the revision was nearing completion, the emerging role of AI (artificial intelligence) in writing, editing, and publishing prompted some additional changes. Chapter 4 now addresses the relationship between copyright and AI. In chapter 3 we show how to credit images created with AI. And chapter 14 now includes examples of how to cite text generated by a chatbot or similar tool. (As AI continues to move into publishing workflows, we will be taking notes for the next edition of the Manual while keeping our readers up to date through our Q&A and at CMOS Shop Talk.)
These and the many other updates for this edition (listed in more detail at CMOS Online) have been considered in light of the long history of this manual and the continuing debt we owe to the collective wisdom of previous generations. Publishing may forever be in a state of flux, but the principles of clarity and consistency—combined with an attention to detail—never go out of style.