Comparisons of pre- and post-depletion nitrogen prescriptions for the BY17 and the JY20 models. Both the input prescription and the output prescription modified by dust depletion are shown. The JY20 model adopts thesame pre-depletion nitrogen prescription as Dopita et al. (2013) and depletes the elements using the CLOUDY default depletion set. The B17 model follows Dopita et al. (2000) for both the pre-depletion nitrogen prescription and the depletion pattern. While the left panel shows the N/O ratios as functions of the absolute oxygen abundance 12 + log(O/H), the right panel shows the N/O ratios as functions of the relative oxygen abundance [O/H], normalized by the solar O/H adopted by each model. The solar oxygen abundances, 12 + log(O/H)_⊙, adopted by Dopita et al. (2000) and Dopita et al. (2013) are 8.93 and 8.69 and indicated by the orange triangle and the cyan star in the plot, respectively.