# Copper has a specific gravity of 8.9: what does this mean?

By definition, the specific gravity (or relative density) of a material is a ratio of the density of that material to the density of water at ${4}^{\circ} C$ which is the temperature at which water has its maximum density.
Ie. SG_s=rho_(rel)=rho_s/(rho_(H_2O at 4^@C).
So if copper has a relative density of 8.9, it means that at ${4}^{\circ} C$, copper is 8.9 times more dense than water.