The so-called apparent density is actually the bulk density.
This is a quantity used essentially with substances in granular form (powders) in order to give an account of the mass of material contained in a given volume, taking into account the volume of interstitial air.
From this point of view, the density or bulk density of the same granulated material can vary depending on whether it is more or less compacted.
In order to respect the unit of the international system, this density, commonly called apparent density, is expressed in grams per cubic centimeter (g/cm3).
The apparent density is measured with a densimeter.