A partial derivative is used for multivariable functions, e.g. , to differentiate with respect to a single input variable, while holding all other inputs constant. The nondifferentiated inputs are not any particular constant, they simply just are not varying. In practice, this means that they behave as constants. By extension, this works in reverse, i.e. with antiderivatives.
Notation
The partial derivative of with respect to
Properties
Clairaut's Theorem
All orders of partial differentiation yield the same result. e.g.
A consequence of this is that you can chose a specific order of differentiation that is easiest.
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