Ratio of the linear (solid lines) and non-linear (dashed lines) power spectra of several CWDM models to that of a pure ΛCDM model with the same cosmological parameters, parameterised by the fraction f_wdm and the rescaled mass x. The other parameters (Ω_dm, Ω_b, h, A_s, n_s) are kept fixed. All spectra are computed today (z = 0). These plots cover all the cases in which WDM has a Fermi–Dirac distribution possibly rescaled by a factor χ, including the limits of the thermal WDM (χ = 1) and Dodelson–Widrow (T_wdm = T_ν) models. In the latter case x coincides with the physical mass. The non-linear spectra are predicted by the emulator introduced in Sect. 3.1 and plotted up to the maximum wavenumber at which this emulator is trusted.