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What Obama is steadily doing to the US dollar. 

Devaluation in modern monetary policy is a reduction in the value of a currency with respect to those goods, services or other monetary units with which that currency can be exchanged. ‘Devaluation’ means official lowering of the value of a country's currency within a fixed exchange rate system, by which the monetary authority formally sets a new fixed rate with respect to a foreign reference currency. In contrast, depreciation is used to describe a decrease in a currency's value (relative to other major currency benchmarks) due to market forces, not government or central bank policy actions. Under the second system central banks maintain the rates up or down by buying or selling foreign currency, usually USD. The opposite of devaluation is called revaluation.
Depreciation and devaluation are sometimes incorrectly used interchangeably, but they always refer to values in terms of other currencies. Inflation, on the other hand, refers to the value of the currency in goods and services (related to its purchasing power). Altering the face value of a currency without reducing its exchange rate is a redenomination, not a devaluation or revaluation. http://en.wikipedia.org/wiki/Devaluation

Currency devaluation is a reduction of the value of a country's currency with respect to currency of another country.