What Is a Robot?

Editor's note: This is the first entry in a new video series, HardWIRED: Welcome to the Robotic Future, in which we explore the many fascinating machines that are transforming society. And we can't do that without first defining what a robot even is. When you hear the word "robot," the first thing that probably comes to mind is a silvery humanoid, à la The Day the Earth Stood Still or C-3PO (more golden, I guess, but still metallic). A robot can be a lot of things these days―and this is just the beginning of their proliferation. With so many different kinds of robots, how do you define what one is?