In physics,<unk>  is mass m per unit volume V—how heavy something is compared to its size. A small, heavy object, such as a rock or a lump of lead, is denser than a lighter object of the same size or a larger object of the same weight, such as pieces of cork or foam.
For the common case of a homogeneous substance,<unk>  is expressed as:
where, in SI Units:
Density
Fluency
Molecular mass
Intensity 
Saturation 
Tonality
Chemical polarity
Pressure gradient 