Question

Defination of relative density?

Answer 1

Relative density

Is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material.
Specific gravity usually means relative density with respect to water.
The term "relative density" is often preferred in scientific usage.
It is defined as a ratio of density of particular substance with that of water.

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Answer 2

the ratio of density of a substance to the density a standard. usually water for liquid or solid and air for a gas.