Abbreviations

Q. Dear CMOS: In your style guide you write that there is no space between a number and the % symbol. But in math it’s normal to put a space between a number and a symbol. It’s also part of ISO and NIST and other standards. Why don’t you follow these standards?

Q. Hi. In Chicago Style, are “T” and “F” acceptable for “True” and “False”? The document is simple questions with T and F answers.

Q. Is there any chance that “am” and “pm” will become acceptable as correct forms of “a.m.” and “p.m.”?

Q. What is the convention for abbreviating thousands, millions, and billions in monetary amounts? I have seen K, M, and B, but I’ve also seen millions represented by MM and thousands represented by M. Thanks!

Q. CMOS omits periods after any designator for United States organizations of any kind—e.g., US Army, US Navy, US Department of State. This format directly contradicts all official U.S. government writing guidelines. What prompted CMOS to make such a change?

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”?

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”?

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!

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)?