In
calculus, the
differential represents the principal part of the change in a function
y =
f(
x) with respect to changes in the independent variable. The differential
dy is defined by
![](http://info.babylon.com/onlinebox.cgi?rt=GetFile&uri=!!ARV6FUJ2JP&type=0&index=1713)
where
![](http://info.babylon.com/onlinebox.cgi?rt=GetFile&uri=!!ARV6FUJ2JP&type=0&index=3041)
is the
derivative of
f with respect to
x, and
dx is an additional real
variable (so that
dy is a function of
x and
dx). The notation is such that the equation