Observed chemical abundances of all known N-emitters including GN-z9p4. Top: N/O versus O/H, bottom: C/O versus O/H. GN-z9p4 is shown by a black star. The N-emitters are sorted by increasing redshift in the legend. Only one measurement (for the densest region) is shown for GS_3073. For Mrk 996, two N/O are available, probing regions of low and high density (James et al. 2009). Low-z star-forming galaxies and HII regions from the compilation of Izotov et al. (2023) are shown by small black symbols. The dash-dotted line shows the average trend observed in low-z star-forming galaxies, as parametrized by Vila-Costas & Edmunds (1993) for N/O and C/O by Dopita et al. (2006), respectively.