The top panel shows the absolute G-band magnitude vs. stellar mass for main-sequence stars, from M. J. Pecaut & E. E. Mamajek (2013, and online updates). The best-fit fourth-order polynomial is plotted in red. The blue curve is the best-fit single-parameter function ﹩{L}_{G}\propto {M}_{\star }^{4}﹩ or, equivalently, ﹩{M}_{G}\,=\,-10{{\mathrm{log}}}_{10}({M}_{\star }/{M}_{\odot })\,+\,C﹩. The bottom panel shows the derivative dM_G/dM_⋆, in units of ﹩{M}_{\odot }^{-1}﹩, which is needed to convert the luminosity function into a mass function (MF).