Comparison of the chemical trends of [X/H]–[Fe/H] between M dwarfs and GK dwarfs, based on Figs. 5 and 6. The underlying colourful dots in density represent the selected (original) sample of GK dwarfs, with their typical error bars shown in the lower right corner of each panel. The overlying orange dots (with error bars) represent the selected (original) sample of M dwarfs. The darker and lighter shaded wedges of individual regression lines represent their 1σ and 2σ error intervals, respectively. Here, we only show the cases for C, O, Mg, and Si; the full set of comparisons of these chemical trends for all elemental pairs can be found in Fig. B.8.