Density

Density: The term density of a substance is defined as the mass of substance (m) per unit volume (V). It is denoted by Greek letter ρ (rho).

$\rho = \frac {mass}{volume}$

The SI Unit for Density is $kg/m^3$. Another commonly used unit is $g/cm^3$.

Density is a characteristic property of any pure substance. Objects made of a particular pure substance such as pure Gold can have any size or mass but the density will remain the same.

Relative Density: It is the ratio of the density of a substance to the density of a pure water at $4 \; \degree C$. It is also known as Specific Gravity.

$Relative \; Density = \frac{Density \; of \;substance} {Density\; of \; water}$