physicsa partial differential equation describing wave motion. It has the form ∇²φ = (1/ c ²) × (∂²φ/∂ t ²), where ∇² is the Laplace operator, t the time, c the speed of propagation, and φ is a function characterizing the displacement of the wave

A partial differential equation that describes the shape and movement of waves, given a set of boundary conditions (such as the initial shape of the wave, or the evolution of a force affecting the wave).

The fundamental equation of wave mechanics. See also Schrödinger's equation.