CCommunity
Relative density of a body is defined as the ratio between the densities of the body to the density of water at 4°C (1 g/cm3or 1000 kg/m3).
$(Relative\:density = \frac{{Density\:of\:milk}}{{Density\:of\:water}} = \frac{{1.03}}{1} = 1.03)$
Unit: Since the relative density is a ratio of two densities, it has no unit.