Q. In CMOS 10.3, I am confused by the meaning of the following sentence, describing “less familiar abbreviations”: “Such an abbreviation should not be offered only once, never to be used again, except as an alternative form that may be better known to some readers.” Would you please clarify? Thank you!

Q. I have two questions about the use of AD (anno Domini). First, is it acceptable to leave the abbreviation after the year when it refers to a decade, as in “the 30s AD” (referring to the fourth decade)? Or should that be “the AD 30s”? Second, since AD literally means “in the year of the Lord,” should we avoid saying “in AD 60,” etc., just as we avoid saying “in ibid.”?

Q. Is it AKA, aka, or a.k.a.? What about in dialogue?

Q. CMOS 10.39 says this: “Where space restrictions require that the names of months be abbreviated, one of the following systems is often used.” How do you suggest one defines “space restrictions”?

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”?