The ability of air (or a substance) to have its molecules reduced in size or volume by pressure.

is the factor of a gas or a gas mixture that causes it to differ in volume from that of a perfect gas when each is under the same pressure and temperature conditions. Occasionally it is called deviation. It must be determined experimentally.

For a fluid, the fractional change in density per unit change in pressure. The compressibility of pure water at 20ºC is approximately 4.47x10-10 kg/(m·s2)-1. For a solid, minus the fractional change in volume per unit change in intergranular stress. Compressibilities range from about 10-10 kg/(m·s2)-1 for sound bedrock to about 10-7 kg/(m·s2)-1 for clay. See also storativity.

Property of a soil pertaining to a decrease in the volume of a soil mass resulting from the expulsion of only pore water when subjected to load.

the change in volume of a unit of volume of a fluid when subjected to a unit change of pressure.

is the change in volume or density due to a change in pressure.

A property of soil which permits deformation when subjected to a load.

property of liquid, solid, and gaseous phases to decrease their volume under applied (isotropic) pressure

Degree of change in volume when a filter is subjected to pressure.

The ability of soil to change volume.

The change in volume of a fluid or solid when subjected to pressure.

Volumetric strain per unit change in hydrostatic pressure.

Degree of physical change in a filter cake when it is subject to pressure, resulting in increased differential pressure and reduced flow.

The relative volume reduction that geological material can undergo when a force is applied or water is removed from the vicinity by pumping.

The condition that the volume of a closed system decreases as the pressure on its surfaces increases. All physical substances are compressible, but the compressibility of liquids and solids is much smaller than for gases. The compressibility of a gas is defined by its equation of state, approximated adequately for many purposes by that for an ideal gas. See coefficient of compressibility; compare incompressibility.

A factor used by fan manufacturers to correct performance rating in higher pressure ranges to account for the fact that air is a compressible gas that does not follow the perfect gas laws.

the property of exhibiting compression under stress In the case of sheet material, the percent of loss of thickness when subjected to a given load applied by a disc of a given diameter for a specified short time and at a specified temperature as defined according to ASTM F-36 test procedures