Comparison of the selected samples of (thin-disc) GK dwarfs (the density plot in the background) and M dwarfs (the overlying orange dots) in the [X/H]–[Fe/H] space. The sample sizes of GK and M dwarfs are shown in each diagram, along with the corresponding test parameters (r and p-value) of Pearson‘s linear correlation (Schober & Schwarte 2018). For reference, the typical error bars of the GK dwarf abundances ([X/H] vs. [Fe/H]) are shown in the lower right corner of each panel, and the zero point of each panel is indicated by the horizontal and vertical dashed lines, along with the diagonal line of the panel. Here, we show only the cases for C, O, Mg, and Si; the full set of comparisons for all elemental pairs can be found in Fig. B.3.