A copier is a machine that makes exact duplicates of documents and images on paper. When you need multiple copies of a permission slip, a teacher places the original in the copier, presses a button, and moments later has thirty identical copies to send home with students.

Modern copiers work by scanning the original document with bright light and transferring the image onto fresh paper using heat and a special powder called toner. Before copiers became common in the 1960s, people had to retype documents multiple times or use messy carbon paper to make copies.

The word can also mean a person who imitates or copies others. If someone always dresses like you, talks like you, and repeats your ideas, you might call them a copycat or a copier, though that can sound insulting.