1. Spatial frequency (k); the number of complete wave cycles per unit distance, and the inverse of wavelength (λ), such that k = 1/λ.
2. Propagation constant; in electromagnetic theory, wavenumber is defined as 2π/λ, and k2 = μω(∈ω + iσ) for the time factor e−iωt, where μ is the magnetic permeability, ω the angular frequency in radians per second, ∈ the dielectric permittivity, and σ the electrical conductivity.
"wavenumber." A Dictionary of Earth Sciences. . Encyclopedia.com. (September 19, 2018). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/wavenumber
"wavenumber." A Dictionary of Earth Sciences. . Retrieved September 19, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/wavenumber