Anything can be compressed. Nevertheless, the difference in compressibility between liquids and gases is huge. Gases can be compressed with small pressures so

Anything can be compressed. Nevertheless, the difference in compressibility between liquids and gases is huge. Gases can be compressed with small pressures so that their volume is reduced to a small fraction of the original volume, while applying great pressures to a liquid will result in a volume only slightly smaller than the original volume. The compressibility of gases can never be neglected, while in many practical applications of liquids it is possible to approximate them as ideal liquids, which are incompressible. The approximation of incompressible liquids is like the approximations of inextensible wires, inextensible membranes or rigid bodies. Even if such ideal objects do not exist, such models simplify the solutions of problems and for many practical cases the solutions are close enough to the solutions that would take into account the deformations or volume changes of the bodies.