What term describes the density of an object relative to water?

The term that describes the density of an object relative to water is specific gravity. Specific gravity is defined as the ratio of the density of a substance to the density of a reference substance, which is usually water at a specified temperature (typically 4°C, where the density of water is at its maximum). Since density is a comparison of mass to volume, specific gravity provides a dimensionless number that indicates how much heavier or lighter a substance is compared to water.

When an object has a specific gravity less than one, it is less dense than water and will float. Conversely, a specific gravity greater than one indicates that the object is denser than water and will sink. This fundamental concept is crucial in various applications, such as material selection, buoyancy calculations, and understanding fluid dynamics.

Other terms like specific weight, liquid density, and relative density may relate to density concepts but do not precisely refer to the comparison between an object's density and that of water as specifically as specific gravity does.