]> SWEET Ontology 1. The ratio of the mass of any substance to the volume occupied by it (usually expressed in kilograms per cubic meter, but any other unit system may be used); the reciprocal of specific volume. 1. The ratio of the mass of any substance to the volume occupied by it (usually expressed in kilograms per cubic meter, but any other unit system may be used); the reciprocal of specific volume. The density of a unit of water after it is raised by an adiabatic process to the surface, i.e., determined from in-situ salinity and potential temperature (AGI, 1980). Density that would be reached by a compressible fluid if it were adiabatically compressed or expanded to a standard pressure. The vertical integral of the density of absorbers between two altitudes; used mainly in determining the transmission through an absorbing gas.