APOGEE chemical plane at the “solar circle” (7 <R_med < 9 kpc) for the Gold sample. To avoid spurious [α/M] data, we only show stars satisfying χ² < 10 and 4000 <T_eff < 5000 K. A possible (purely chemical) definition of thin and thick discs, consistent with, e.g., Lee et al. (2011), is indicated by the division into the black points and grey triangles, and the dashed line. For comparison, we also plot kinematically selected candidate bulge stars (big hexagons).