There are three types of boundary conditions commonly encountered in the solution of partial differential equations:
1. Dirichlet boundary conditions specify the value of the function on a surface .
2. Neumann boundary conditions specify the normal derivative of the function on a surface,
3. Robin boundary conditions. For an elliptic partial differential equation in a region , Robin boundary conditions specify the sum of and the normal derivative of at all points of the boundary of , with and being prescribed.