Density is the mass of an object per unit volume, whereas relative density is the ratio of the density of an object to the density of a reference material (usually water).
- Density is the mass of a unit volume and relative density is the
ratio of the density of a substance to the density of the reference material.
- Density has units but relative density does not.
- Density may have different numerical values depending on its units but relative density has a constant value.