Below is the graph of the function y = 2x. Given any x, it just doubles the value.

This function obviously has slope, and plenty of it. Since y rises twice as fast as x, it's said to have a slope of 2. This means that its first derivative is 2, or:

If this function had been y = 3x, its graph would rise even faster; it would have a derivative of 3:

In general:

For any given constant n.