**dy/dx and dy is another way of representing a function's derivative (in this case, ***y* is the function and the derivation variable is *x*)

remember the definition of a function's derivative?

but

so we can put the definition like this:

now call the numerator "differential in y", **dy**

and the denominator "differential in x", **dx**

as you can see in the above expression, a function's derivative can now be expressed with the help of differentials (infinitely small *increments*)

So as you can see **dy/dx** is the derivative of **y=f(x) with respect to x**

You cand understand this easly if you recall that the derivative of a function is related to the slope of the its tangent line on a certain point. And how do you find slopes? With quotients between the y-increments and x-increments!

The difference is that dy and dx are very small increments.. so small you can only express them using *limits*

...understanding differentials is a major step to any calculus student imho! Then you can move on to more complex topics like integration and **differential** equations.

!)