for: a periodic wave of wavelength
is defined: as 
[M6.4, P5.6]
has as its SI unit: 
(i.e. per metre). [M6.4, P5.6]
is widely referred to: as the wavenumber, though this latter term is more properly reserved for 
i.e. 
[M6.4, P5.6]
See also angular wave vector and compare with angular frequency. [M6.4, P5.6]
Copyright 1997, The Open University