NCIt definition : The density (mass per unit volume) of any material divided by that of water at a standard
temperature.;
Alternative definition : CDISC: A ratio of the density of a fluid to the density of water.; PQCMC: The ratio of the density of any substance to the density of some other substance
taken as standard, water being the standard for liquids and solids, and hydrogen or
air being the standard for gases.;