Definition:Boundary Condition

Definition
Let $\Phi$ be a differential equation to which a solution is to be found.

A boundary condition is an equation relating particular values of the dependent and independent variables which the solution to $\Phi$ must satisfy.

It is usual for such boundary conditions to correspond to the physical extremities of bodies, aspects of whose internal nature is being modelled by means of $\Phi$.

Also see

 * Definition:Initial Condition