Cotangent space

Cotangent space is a space that tells you how two things are related by measuring the angle between them. It's like a see-saw with two sides: when one side goes up, the other one goes down. The angle between the two sides is what the cotangent space measures. This angle is like a measure of how different two things are. For example, if two things have an angle of 90°, then they're very different from each other. If the angle is small, then the two things are similar.