Definition:Heat Equation

Equation
The heat equation is a second order PDE of the form:
 * $a^2 \left({\dfrac {\partial^2 w} {\partial x^2} + \dfrac {\partial^2 w} {\partial y^2} + \dfrac {\partial^2 w} {\partial z^2}}\right) = \dfrac{\partial w} {\partial t}$

Also see

 * Solution to Heat Equation