Mass concentration (chemistry)

In chemistry, the mass concentration ρ_i (or γ_i) is defined as the mass of a constituent m_i divided by the volume of the mixture V.

${\displaystyle \rho _{i}={\frac {m_{i}}{V}}}$

For a pure chemical substance, the mass concentration equals its density (mass divided by volume); thus the mass concentration of a component in a mixture can be called the "density of a component in a mixture". This explains the usage of ρ (the lower case Greek letter rho), the symbol most often used for density.