Relative enrichment of nitrogen and the α elements. Light gray circles represent direct abundances taken from Bresolin et al. (2005, 2009a, 2009b), Croxall et al. (2009), Esteban et al. (2009), Kennicutt et al. (2003), Peimbert et al. (2005), Testor (2001), Testor et al. (2001), Zurita & Bresolin (2012), and Berg et al. (2015). (Top)–(Bottom): log(N/O) as a function of oxygen abundance. The dotted line designates the theoretical curve of Vila-Costas & Edmunds (1992), the black dashed line is the empirical linear fit to galaxies from Pilyugin et al. (2010), the black dotted–dashed curve is the quadratic fit from Pilyugin et al. (2010), the blue dashed line is the scaled model fit from Groves et al. (2004); log (S/O) as a function of oxygen abundance; log (Ne/O) as a function of oxygen abundance; log (Ar/O) as a function of oxygen abundance. In the three lower panels, the dashed line in each panel denotes the mean value for our observations of NGC 5457. Additionally, we have marked the locus of the population of H II regions with log(Ne/O) ≈ −1.0 using a dashed red line.