the falling of value.

a lessening in value, importance, etc.

depreciation - a) a decrease in value of property through wear, deterioration or obsolescence; b) the allowance made for this in book-keeping, accounting, etc.

the devaluation of currency - a) an instance of reduction in the amount or fineness of a metal, esp. gold, officially designated as the standard of value of a monetary unit; b) an official lowering of the exchange value of a currency with reference to other currencies.