Q. I am seeing everywhere now that people are putting acronyms in parentheses instead of words, as in “Food and Drug Administration (FDA)” versus “FDA (Food and Drug Administration).” Can you explain to me why this is becoming more common? Parentheses have always been intended for additional information or words of further explanation, which is the opposite of an acronym. It just seems so backwards to me, and if you’re searching for what the acronym stands for, it’s hard to find because the acronym is in the parentheses and used from then on. Please help me understand the logic people are following with this style.

Q. What is the stance of CMOS on single-letter abbreviations for days of the week? In US higher education, the single-letter abbreviations (M, T, W, R, F, S, U) are ubiquitous, though I find no mention of these abbreviations being codified (ISO uses numbers). In prose, I often find myself using these abbreviations in lists of upcoming deadlines.

Q. When should you capitalize AM and PM?

Q. How do I abbreviate the word “number”?

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.