The question mark is used at the end of a direct question. Indirect questions take a period.
Direct question: What is she doing tonight?
Indirect question: I wonder what she’s doing tonight.
Direct question: The question is, Does anyone support this legislation?
Indirect question: The question was whether anyone supported the legislation.
When a direct question occurs within a larger sentence, it takes a question mark. Note that in the examples below, the question mark supplants the comma that would syntactically belong in its place.
Would they make it on time? she wondered.
The key question, Can the two sides reach a compromise? was not answered.
“What are we having for dinner?” his son asked.
In contrast with the examples above, when the question mark is part of a title of work, a syntactically necessary comma is retained.
Have you read Do Androids Dream of Electric Sheep?, the Philip Dick novel that inspired the movie Blade Runner?
“Is He Living or Is He Dead?,” by Mark Twain, is one of my favorite stories.
When the question mark in the title comes at the end of a sentence that would itself require a question mark or period, the additional question mark or period is omitted.
Have you read Do Androids Dream of Electric Sheep?
I have not read Mark Twain’s “Is He Living or Is He Dead?”
Requests that are phrased as questions should end with a period.
Would you please send this report to the person indicated on the cover.
The question mark can be used to indicate editorial uncertainty, either in parentheses or in brackets. Some authorities include a space between the uncertain word and the opening parenthesis; others omit the space (as shown in the example below).
The patient reported taking 15(?) milligrams of alprazolam.
According to his biographer, Smith “bought the company in 1985 [1984?], but wasn’t actively engaged in its management until 1990.”
Use of the question mark with other punctuation, including quotation marks, is explained in the section on terminal punctuation.