Specific density is the ratio of the mass versus the volume of a material.
Density vs. gravity
Specific density is based upon units of mass and volume, while
specific gravity
Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water (molecule), wa ...
is dimensionless.
References
Physical quantities
Density
Volume
Ratios
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