Depletion
Depletion may refer to:

Environment
Resource depletion, decline of resources
Gas depletion, decline of oil supply
Nutrient depletion, loss of nutrients in a habitat
Oil depletion, decline of oil supply
Overdrafting, extracting groundwater beyond the equilibrium yield of an aquifer
Ozone depletion, a decline in the total amount of ozone in Earth's atmosphere

Physics
Depletion force, an effective force in molecular and colloidal systems
Depletion region, in semiconductor physics
Grain boundary depletion, a mechanism of corrosion

Other uses
Ego depletion, idea that self-control or willpower draws upon a limited pool of mental resources that can be used up
Depletion (accounting), an accounting and tax concept used in mining, timber, petroleum, or other similar industries
T-cell depletion, process of T cell removal or reduction