What does Differentiation mean by its word?

Differentiation is the maths of varying variables. In science, what is actually important is not what value something has at the moment, but what value it will have. This is where the differentiation comes in. By differentiating a variable, we get the rate at which it is changing. To start with, we think about the gradients of curves, but soon move on, to apply differentiation to quantities changing with time.