Formula Definition of the Wave Number Wavelength
$$\nu ~=~ \frac{1}{\lambda}$$ $$\nu ~=~ \frac{1}{\lambda}$$ $$\lambda ~=~ \frac{1}{\nu}$$
Wavenumber
$$ \nu $$ Unit $$ \frac{1}{\mathrm{m}} $$ Wavenumber indicates how many times the wavelength of a periodic wave fits into one meter.
Wavelength
$$ \lambda $$ Unit $$ \mathrm{m} $$ Wavelength is the smallest distance between two points of the same phase of a periodic wave. For example, the wavelength is the distance between two wave crests.