To reply means to answer someone or respond to what they've said or written. When your teacher asks a question and you raise your hand to give an answer, you're replying. When you write back to a friend's email or text message, you're sending a reply.

A reply can be quick and simple, like saying “yes” when someone asks if you want pizza, or it can be longer and more thoughtful, like writing a detailed response to a pen pal's letter. The key is that you're responding to something specific that someone else started.

Sometimes people use reply more formally than answer. You might answer your mom when she calls you for dinner, but you reply to a wedding invitation or reply to your principal's email. The word often appears in writing: “Please reply by Friday” or “I'm waiting for his reply.”

You can also reply to actions, not just words. If someone waves at you and you wave back, you're replying to their greeting. When an audience applauds and the performer bows, that bow is a kind of reply.