The Voigt profile is the convolution of a Lorentzian (natural/pressure broadening) and a Gaussian (Doppler/thermal broadening). It appears in atomic spectroscopy, NMR, and X-ray diffraction. The Lorentzian has power-law wings; the Gaussian has exponential falloff. Their convolution — computed via the Faddeeva function w(z) = e^{−z²}erfc(−iz) — interpolates between both limits and is the physically correct line shape for most spectroscopic situations.