A wave that propagates, typically, on the surface of water under the influence of buoyancy forces. In water of uniform depth H, the dispersion relationship is given by squared frequency omega^2 = gk tanh(kH), in which k is the wavenumber and g is the acceleration of gravity. In shallow water, when the wavelength is much larger than the fluid depth, the waves are nondispersive: the dispersion relationship is omega = c k, in which phase speed c=(gH)^(1/2). In deep water the waves have dispersion relationship omega = +/- (gk)^(1/2).