Definitions for "H-R diagram"
a plot of stars that shows their relative brightness and temperature; first developed by Enjar Hertzsprung and Henry Norris Russell.
A plot of luminosity versus temperature for a group of stars that can be used to classify the evolutionary state of stars.
A plot of the intrinsic brightness versus the surface temperature of the stars. It separates the effects of temperature and surface area versus spectral type, but also luminosity versus surface temperature or color.