The question mark (?; also known as an interrogation point, interrogation mark, question point, query or eroteme), is a punctuation mark that replaces the full stop (period) at the end of an interrogative sentence in English and many other languages. The question mark is not used for indirect questions. The question mark character is also often used in place of missing or unknown data.
Origin: Long ago when scholars wrote in Latin, they would place the word questio – meaning “question” at the end of a sentence to indicate a query. Soon questio was shortened to qo to save space when writing, but this caused a different problem – readers might mistake it for the ending of a word. So they squashed the letters into a symbol (a lowercased q on top of an o). Over time the o became just a dot and the q changed into a squiggle, giving us our current question mark.
* Try not to use question marks with other marks. It is considered bad to use a question mark in combination with other marks. In Japan, you may see this type of usage in manga books. Especially when translated from Japanese into English → !?
Question marks can be used with other marks in informal prose to convey complex tones though: He told you what!? This combination (or similar combination) of punctuation marks is sometimes called an interrobang. The interrobang currently has no role in academic prose though.
Rule 1. Use a question mark only after a direct question.
Correct: Will Akiko go with me?
Incorrect: I’m asking if Akiko will go with me?
Rule 2a. A question mark replaces a period at the end of a sentence.
Incorrect: Will you go with me?.
Rule 2b. Because of Rule 2a, capitalize the word that follows a question mark.
Some writers choose to overlook this rule in special cases.
Example: Will you go with me? with Joe? with anyone?
Rule 3a. Avoid the common trap of using question marks with indirect questions, which are statements that contain questions. Use a period after an indirect question.
Incorrect: I wonder if Glen would go with me?
I wonder if Glen would go with me.
I wonder: Would Glen go with me?
Rule 3b. Some sentences are statements—or demands—in the form of a question. They are called rhetorical questions because they don’t require or expect an answer. Many should be written without question marks.
Why don’t you take a day off.
Would you kids knock it off.
What wouldn’t I do for you!
Rule 4. Use a question mark when a sentence is half statement and half question.
Example: You do drink, don’t you?
Rule 5a. The placement of question marks with quotation marks follows logic. If a question is within the quoted material, a question mark should be placed inside the quotation marks.
She asked, “Will it still be my turn?”
The question Will it still be my turn? is part of the quotation.
Do you agree with the saying, “All’s fair in love and war”?
The question Do you agree with the saying? is outside the quotation.
Rule 5b. If a quoted question ends in mid sentence, the question mark replaces a comma.
Example: “Will it still be my turn?” she asked.