Mass-loss rate as a function of stellar luminosity for the analysed O stars in NGC 346. Luminosity classes are distinguished by different colours as given in the legend. A power-law fit to the empirical results is represented by the blue solid line (see Sect. 4.2 for details). For comparison, we include stars with from UV observations from Ramachandran et al. (2019) (circles), two additional objects within NGC 346 with from Bouret et al. (2003) (squares) and the theoretical SMC predictions from Vink et al. (2000, 2001) (dashed blue line), Krtička & Kubát (2018) (black dashed line) and Björklund et al. (2021) (dashed red line).