Aging

[1] The cracking, checking, or general deterioration produced by exposure of an adhesive, coating or sealer to the weather or some other given set of conditions for a length of time
[2] The deterioration of rubber properties by oxidation over a period of time.
[3] A change in the properties of some metals after heat treatment or cold working (i.e., hammering or bending when metal is cold).
[4] The final stage of precipitation hardening, producing an increase in strength and hardness in metal alloys, due to precipitation of second phase particles from supersaturated solid solution over a period of days at room temperature, or several hours at an elevated temperature (called artificial aging)
[5] Loss of strength in the cladding or the pressure vessel in a nuclear reactor due to irradiation. Artificial aging would be the simulation of such processes by increasing the rate of irradiation to obtain information more rapidly
[6] Change in the properties of a substance with time. A change in the magnetic properties of iron, e.g., increase of hysteresis loss of sheet-steel laminations; also the process whereby the subpermanent magnetism can be removed in the manufacture of permanent magnets
See also artificial aging, tire aging