柯林斯詞典relative density 1. N the ratio of the density of a substance to the density of a standard substance under specified conditions. For liquids and solids the standard is usually water at 4°C or some other specified temperature. For gases the standard is often air or hydrogen at the same temperature and pressure as the substance 相對密度 ( symbol: )→see also specific gravity , vapour density 返回 relative density劍橋詞典the mass of a particular volume of a substance when compared with the mass of an equal volume of water at 4°C 相對密度 返回 relative density