Dual space

Dual space is a mathematical concept that is used to describe how two things relate to each other. It's kind of like a mirror image, where one thing is the original, and the other is the reflection. Everything in the original is also in the reflection, just in a different way. Let's say you had a picture of a bird flying. In dual space, the bird would be mirrored, and flying in the opposite direction. That way, you can see how the two halves of the picture connect to each other.