What is compressibility?

Compressibility is the capacity of a substance to be reduced in volume by the application of a pressure. It is a measure of the ease with which a substance can be compressed by a relative decrease in its volume. A material's compressibility is usually related to the fractional change in volume associated with a given change in pressure. Compressibility of a substance is more a function of physical characteristics, such as its internal structure, than its chemical composition.