DEFINED as the ratio of the density, MASS or weight of the substance to the density, mass or weight of water at 4° C\(Relative\;density = \FRAC{{Density\;of\;substance\;}}{{Density\;of\;water\;at\;4^\circ C}} \approx \frac{{Mass\;of\;substance\;}}{{Mass\;of\;water\;at\;4^\circ C}} \approx \frac{{Weight\;of\;substance\;}}{{Weight\;of\;water\;at\;4^\circ C}}\)Here relative density is unitless and the density of water at 4° C is 1.0×103 kg/m3Whereas density, \(\RHO = \frac{{Mass}}{{Volume}}\)