Question: The ratio of the wave height to its wave length is called?

context: No context provided
question: What is the ratio of a wave's height and length called?
short_answers: wave steepnes
context: Note that the second- and third-order terms in the velocity potential Φ are zero. Only at fourth order do contributions deviating from first-order theory – i.e. Airy wave theory – appear. Up to third order the orbital velocity field u = ∇Φ consists of a circular motion of the velocity vector at each position ("x","z"). As a result, the surface elevation of deep-water waves is to a good approximation trochoidal, as already noted by .
question: What is the theory used to describe the ratio of a wave's height and length?
short_answers: Airy wave theory

Answer: In fluid dynamics, a Stokes wave is a nonlinear and periodic surface wave on an inviscid fluid layer of constant mean depth. The ratio of a wave's height and length is called wave steepness. Airy wave theory describes the ratio of a wave's height and length.