Derivative

The instantaneous rate of change of a function
f (x)
at a particular point
x
_{0}
, denoted
f'(x
_{0})
or
(x
_{0})
. The formal definition is the following limit:
f'(x
_{0}) =


Derivative Function

A function
f'(x)
taking on the value of the derivative of
f (x)
at each number
x
.
Difference Quotient

For a function
f
, and any two points
x
_{0}
and
x
in its domain, the quotient:
Differentiable

A function
f
is differentiable at a point (
x
_{0}
) if it has a welldefined derivative
at that point. It is simply differentiable if it is differentiable at every point in its
domain.
Secant Line

A line through two distinct points on the graph of a function.
Tangent Line

A line through a point
(x, f (x))
on a graph that has slope equal to the derivative of the
function
f
at
x
. A limit of secant lines to the graph of a function as two contact
points approach one another.