Q. How would I punctuate the end of a sentence that ends with an abbreviation? For example, “I attended a meeting at ABC, Inc.” Two periods don’t look right.

Q. When ending a sentence with an abbreviation, do you need two periods? The event was held in Washington D.C..

Q. When the author has a middle initial are two periods used in a bibliography? Jordan, Alyce A.. “Rationalizing the Narrative.”

Q. Should one put a period on either side of the parenthesis that ends a parenthetical list ending with “etc.” or just one? Example: We have fruit (apples, oranges, etc.).

Q. In the following sentence, I omitted the period per CMOS 6.124: . . . as shown in the Sony Film Classics 2006 documentary, “Who Killed the Electric Car?”. My colleague, however, said the period should remain, because it belongs to the sentence, not the title of the movie.

Q. My question is about whether or not periods should be placed at the end of a URL used within a sentence. My coworkers say that we don’t need a period at the end of a website address.

A. For some reason, questions about periods have dominated the Q&A mail lately. Why the sudden confusion? Why, after a lifetime (I trust) of never encountering two periods in a row, do readers suddenly think this might be a good idea? In any case, here are some answers: Don’t ever put two periods in a row. Put one period at the end of a declarative sentence, even if it ends with an abbreviation or a URL. (Questions and exclamations use question marks and exclamation points instead of a period, not in addition to one, even in quotations.) A sentence that stands alone within parentheses needs a period inside the parentheses to end it. (Here’s an example.) A sentence in parentheses within another sentence does not take a period, because the period is reserved for the main sentence (questions and exclamations, however, must have their respective marks!). An abbreviation that ends with a period must not be left hanging without it (in parentheses, e.g.), and a sentence containing a parenthesis must itself have terminal punctuation (are we almost done?). Finally, an abbreviation ending with a period that is immediately followed by a question mark or exclamation point requires both marks (Q.E.D.!).