Partial derivative
From Citizendium, the Citizens' Compendium
In mathematics, a partial derivative of a function of several variables is its derivative with respect to one of those variables while all others are kept constant. Partial derivatives are widely used in differential geometry, vector calculus, and physics.
Definition
A function
is called a function of multiple variables if
. The partial derivative of
in the direction
at the point
is defined as
Notation
The partial derivative of a function f with respect to the variable xi is written as fxi or ∂f/∂xi. The partial derivative symbol ∂ is distinguished from the straight d that denotes the total derivative.

