# What is the relationship between mass and volume known as?

It's known as $\text{density}$.
The quotient $\text{mass"/"volume}$ is known as $\text{density, } \rho$, the mass per unit volume. Typically, chemists would use units such as $g \cdot m {L}^{-} 1$. Sometimes you see $\text{relative densities}$ quoted; the density relative to a reference substance, i.e. water, and substances with greater relative density than water should sink,