The main function of a question mark is to indicate a question or query.
1. Use a question mark at the end of all direct questions:
- What is your name?
- How much money did you transfer?
- Did you send euro or dollars?
2. Use a question mark after a tag question:
- You're French, aren't you?
- Snow isn't green, is it?
- He should go and see a doctor, shouldn't he?
3. Don't forget to use a question mark at the end of a sentence that really is a direct question:
- How else would I get there, after all?
- What if I said to you, "I don't love you any more"?
- "Who knows when I'll die?", he asked rhetorically.
4. In very informal writing (personal letter or email), people sometimes use a question mark to turn a statement into a question:
- See you at 9pm?
In the same situation, they may use two or three question marks together to show that they are not sure about something:
- I think you said it would cost $10???
5. Do not use a question mark after an indirect or reported question:
- The teacher asked them what their names were. (What are your names?)
- John asked Mary if she loved him. (Do you love me?)
- I'm wondering if she's coming. (Is she coming?)
6. Many polite requests or instructions are made in the form of a question. But because they are not really questions, they do not take a question mark:
- Could you please send me your catalogue.
- Would all first-class and business-class passengers now start boarding.
7. Be careful with titles and abbreviations when question marks are involved:
- "Who's afraid of Virginia Woolf?" was a play before it was a film.
- Who's afraid of Virginia Woolf? was a play before it was a film.
- Have you seen the film "Who's afraid of Virginia Woolf?"?
- Have you seen the film Who's afraid of Virginia Woolf??
- Have you ever been to L.A.?
Note that there should be no space immediately before a question mark.