A1 used to ask for information about something: What’s (= what is) this? What time is it?
A1 informal used when you have not heard what someone has said and you want him or her to repeat it. Some people think this use is not polite: “Would you like more coffee, Tom?” “What?”
B1 used to mean something without giving it a name: I heard what he said. Do you know what I mean?
› informal used to ask what someone wants when he or she calls your name: “Jenny?” “What?”
what about…? A2 used to suggest something: What about asking Andy to help?
what a/an… B1 used to give your opinion: What an awful day!
what if…? B1 used to ask about something that could happen in the future, especially something bad: What if I miss the plane?
what… for? › used to ask about the reason or the purpose for something: What are these tools for? What are you doing that for?