Derivative

Derivative indicates the change rate of a function at a given moment. The function has to be continuous which means a smooth line without any break points, gaps and jumps. The graph of the function must be able to be draw by only one motion. If the derivative is positive, the function is increasing. When the derivative is negative, the function is decearsing. When the derivative is 0, the function is not changing at this moment. There is no derivative in the discontinuous part of a function. It is a very basic idea in calculus, which can be used in Calculus, Physics and more scientific subjects.