Comparison between average dwarf and giant stars spectra with similar spectral class. The similarities of the two types of spectra increase with increasing the spectral type. The spectra of giants are presented in red and the dwarfs with blue dotted lines. The positions of some of the most characteristic features (upper row for giants, second row for dwarfs) as well as some telluric bands (in the bottom) are shown with black lines. The spectra are shifted along the y-axis with an arbitrary constant for presentation purpose.