Quotations

Q. I’m looking for the etched-in-stone rule that states that a dialogue tag should be lowercase after a question (i.e., “What is it?” she asked, as opposed to “What is it?” She asked). I have both the 15th edition of The Chicago Manual of Style and the trial online version here and have so far been unable to find it. Any help is appreciated.

A. The rule is fundamental: If a word continues a sentence, lowercase it (unless it’s a proper name). If a word begins a new sentence, uppercase the first letter. Thus, if “She” is capped after a quotation (as it sometimes is), it signals a new sentence: “What is it?” She asked three times before she gave up.