Wavenumber

In the physical sciences, the wavenumber is the spatial frequency of a wave. It can be envisaged as the number of waves that exist over a specified distance (analagous to frequency being the number of wave oscillations that take place in a specified time). More formally, it is the reciprocal of the wavelength.

It is also the magnitude of the wave vector.

Read more about Wavenumber:  Definition, In Wave Equations, In Spectroscopy