A Lorentzian line shape function can be represented as
where L signifies a Lorentzian function standardized, for spectroscopic purposes, to a maximum value of 1;  is a subsidiary variable defined as
where  is the position of the maximum (corresponding to the transition energy E), p is a position, and w is the full width at half maximum (FWHM), the width of the curve when the intensity is half the maximum intensity (this occurs at the points ).  The unit of ,  and  is typically wavenumber or frequency. The variable x is dimensionless and is zero at .