Q. My publisher prefers that AD come before the year (as in “AD 99”), but would the same rule apply to centuries? That is, should it be “first century AD” or “AD first century”?
A. The abbreviation AD stands for anno Domini, Latin for “in the year of the Lord,” so the order AD 99 is required for proper syntax: “in the year 99” makes sense; “99 in the year” does not. BC, which means “before Christ” (the English-language complement to AD), naturally follows the year: 99 [years] BC. The problem with AD and centuries is that they don’t mix: “in the year of the Lord first century” and “first century in the year of the Lord” both fail the test. Not to worry. English and Latin were never meant to coexist, and “the first century AD” is a perfectly acceptable way of referring to “the first century after the year 1 BC” (there is no year zero). (The alternative, “the AD first century,” doesn’t quite work.) Some writers use CE ([of the] Common Era) and BCE (before the Common Era), both of which follow the year, but the older abbreviations have persisted and are more likely to be understood by readers. See CMOS 9.34 for some additional considerations.
Q. Does Chicago prefer “COVID-19” or “Covid-19”?
Q. Isn’t it redundant to have an “MBA in business administration”? I thought it was a mistake at first, but a lot of people use this—and perhaps it really is the degree name—but it just seems weird . . . “master of business administration in business administration”?
A. Having an MBA in business administration does sound a little like using a PIN number at an ATM machine to get money to repair your broken LCD display so you can read about RAS syndrome on Wikipedia over a cup of chai tea. But if your colleague has an MBA in marketing or finance, you may want to make your own concentration in business administration explicit. It’s probably best, therefore, to ask before editing out the apparent redundancy.
Q. Once and for all: to abbreviate “postscript” at the end of correspondence, is it best to write PS or P.S.? The glossary in CMOS advises no periods, but several examples in the Q&A use them, like this one. Help!
A. Chicago style for the abbreviation of “postscript” can be deduced from our recommendations for using periods with abbreviations (CMOS 10.4), which can be summarized as follows: (a) use periods for an abbreviation that consists of lowercase letters or that ends in a lowercase letter, such as p. or pp., a.m. or p.m., and Dr.; (b) use a period for an initial standing in for a name, as in E. B. White; but (c) omit periods from abbreviations that include two or more capital letters, such as US, PhD, and CEO.
So we would advise writing “PS,” no periods. (The lowercase alternative, “p.s.,” doesn’t seem to be supported by tradition. And the glossary entry you refer to is for the abbreviation of PostScript, the specialized programming language from Adobe—so that doesn’t count.)
As for our own use of “P.S.”—with periods—guilty as charged. As the Q&A has developed over the last twenty-plus years, Chicago style has evolved. Until 2003, we would have advised periods, but then we dropped them—first from academic degrees and most other abbreviations with capital letters (in the 15th ed.), and then also from “U.S.” (in the 16th ed.).
Another consideration: Postscripts are a little old-fashioned (you can usually go back and edit the body of your letter or email or whatever), and so are periods.
But that’s all in the past. Thanks to your query and others like it, we hereby announce “PS”—no periods—as our preference for “postscript.”
PS: You can follow “PS” with either a colon or a period. With our updated preference, the colon is best, but if you prefer “P.S.” you can leave it out.
Q. I hate defining acronyms in the first paragraph of a paper because they impede flow. Therefore, is it acceptable to repeat the whole phrase, in this case, greenhouse gases, in the second use, and then define it there as (GHG)?
A. See CMOS 10.3: “The abbreviation usually follows immediately, in parentheses, but it may be introduced in other ways.” Your approach seems like a sensible and reader-friendly alternative to introducing the abbreviation immediately after the first mention.
Q. I’m working on some writing that mentions “SQL servers.” I’m wondering whether I should go with “this data is stored on an SQL server” or “a SQL server.” I happen to be aware that “SQL” is usually pronounced “sequel,” which would lead me to write “a SQL server.” However, I worry that anyone unfamiliar with the term would assume each letter is pronounced individually—and it is very likely that the language I’m working with will be seen by many who are unfamiliar with SQL. What do you recommend?
A. You could spell out the pronunciation of SQL at the first opportunity in the text—for example, “this data is stored on a SQL (pronounced ‘sequel’) server” (see also CMOS 10.3). Those who are unfamiliar with this pronunciation (from “Structured English Query Language,” or SEQUEL, the name first proposed in the early 1970s) will now be clued in; those who already say “sequel” will have their preference confirmed. But it should be noted that according to ANSI (the American National Standards Institute), the pronunciation of SQL is not a settled issue, and “ess-cue-el” is considered a legitimate option. So it’s not a bad idea to signal a preference regardless of your choice.
A note on the example: Though “data” is usually plural in scientific contexts—“these data are”—“data” is often used as a mass noun in computer-related writing. For example, this usage is allowed by the latest style guides published by Microsoft and Apple.
Q. Is Q&A an acronym or an abbreviation? When using Q&A in, say, a training in PowerPoint, do you need to write out “Questions and Answers” the first time, like you would in an acronym, or does it stand on its own as Q&A?
A. Q&A is a pair of initialisms joined by an ampersand; as such, it’s an abbreviated form of the abbreviated expression “Q and A.” And because “Q and A” is widely known (and has its own entry in Merriam-Webster), there is no need to spell out either form the first time you use it. For a discussion of acronyms and initialisms (both of which are types of abbreviations), see CMOS 10.2; for the absence of spaces in Q&A, see CMOS 10.10.
Q. Hi, can you tell me what “pl.” stands for in “vol. 5 (1822), pl. 57”? Thanks!
A. It most likely stands for “plate”—as in an illustration printed on special paper and bound together in a separate section known as a gallery; these pages typically aren’t paginated with the rest of the book, so plate or figure numbers must be used instead of page numbers to refer to individual pages in the gallery. CMOS 10.42 includes nearly 250 abbreviations that might appear in scholarly publications, including “pl.” As you will see in that list, the abbreviation “pl.” can mean either “plate” or “plural” but is best avoided for the former. Whoever recorded “pl.” in the example you cite apparently didn’t see our list.
Q. I’m wondering about omitting the periods for US Department of Energy. On its site, it’s U.S. Do we follow the department’s preference or Chicago style?
A. The name of the organization is the United States Department of Energy. When you follow Chicago style to write “US Department of Energy,” you are abbreviating the fuller form of the name. The abbreviation at Energy.gov probably follows the GPO Style Manual, published by the US Government Publishing Office. GPO style uses periods in “U.S.” (and “U.K.” and the like), and those periods are a matter of government style. But unless you’re writing for the government, it is safe to omit them.
Q. What is the proper way to write Dr. Tom Smith Jr., M.D.?
A. Use MD or Dr., but not both. Please see CMOS 10.16 and 10.19. Some style guides use periods in M.D. and put a comma before Jr., but Chicago prefers the following forms:
Tom Smith Jr., MD
Dr. Tom Smith Jr.