Manuscript Preparation, Copyediting, and Proofreading

Q. Dear CMOS, in one of the articles I’m editing, the authors have a list of documents, where each document title is followed by a descriptive phrase. The title and phrase are separated by a colon. (1) Should the first word in the phrase be lowercase? The authors tend to capitalize it, but I think it should be lowercase (unless it’s a proper noun). (2) Would it be more appropriate to use an em dash instead of a colon? Here’s an example:

Guide: Step-by-step instructions to fill out
Best Practices: Frequently asked questions about best practices
Dedicated Observations: Information on dedicated background exposures

A. Although this isn’t a glossary, it behaves like one, so the guidelines for glossaries would probably serve you well. CMOS 2.23 (“Format for Glossaries and Lists of Abbreviations”) suggests a period, colon, or em dash after the entry. CMOS also suggests beginning the definition with a capital letter. (In a list of abbreviations, however, the definition should be uppercased or lowercased according to the meaning of the abbreviation.) Given that there is flexibility, accommodate the writers’ preference if you can.