The specific gravity is defined as the ratio of mass density or weight density of a fluid to the mass density or weight density of a standard fluid.specific gravity based on the it’s value.

(OR)

It is the ratio between the reference substance and density of an object.

- Specific gravity is dimensional less quantity and it is denoted by the “S”

S = Weight density (density) of liquid / Weight density of water

S = Weight density of gas / Weight density of air

## Compressible Fluid:

- Compressible fluid is defined as the fluids which change their density for even a small changes in temperature or pressure are termed as compressible fluids.
- Example of compressible fluid is: Air, Vapour and gases.

## InCompressible Fluid:

- The fluids are defined as the substances for which the density of every particles remains constant at any temperature (or) pressure irrespective of the state of stress.
- Example of Incompressible fluid is:H2O and mercury.