Compression in material science, physics or structural engineering, is the stress state of materials where the volume tends to decrease (compaction).

Compression is the result of the subjection of a material to compressive stress.

There are some indications that astronomical observations of gamma-ray bursts are possibly due to compression (http://www.aas.org/publications/baas/v30n2/aas192/abs/S043014.html) of neutron stars.

In laboratories, compression of materials is achieved by the use of press machines to measure the mechanical properties of materials such as compressive strength or the modulus of elasticity by experiments.

See also: buckling, strength of materials.