Here is what Wikipedia says about devaluation:
http://en.wikipedia.org/wiki/Devaluation
Here is what Wikipedia says about depreciation:
http://en.wikipedia.org/wiki/Depreciation_(currency)
Here is what Wikipedia says about debasement:
http://en.wikipedia.org/wiki/Debasement
Devaluation actually occurs within a fixed exchange rate system. The last time there was a formal devaluation of the U.S. dollar was in 1971 when Nixon told foreign governments that they could no longer redeem their dollars for gold.
Depreciation occurs in a system of floating exchange rates. Wikipedia says that depreciation refers to a decrease in the value of a country's currency with respect to one or more foreign currencies.
When we look at debasement, Wikipedia says it is the practice of lowering the value of a currency. It goes on to say that, "It is particularly used in connection with commodity money such as gold or silver coins. A coin is said to be debased if the quantity of gold, silver, copper or nickel is reduced."
All of these words seem to be used interchangeably. In the entry for "devaluation", Wikipedia says this is incorrect, but that they always refer to values in terms of other currencies. But my question is, how do you refer to an increase in the money supply? This used to be called inflation, but the definition of inflation was changed by the statists to refer to prices (which is actually just the effect of inflation).
I use these terms interchangeably with the knowledge that it is not technically correct in the financial world. But I don't really care about other currencies. You could say that the dollar is not depreciating against the euro, yen or some other currency at some particular time, but that is not helpful if all of the central banks are creating new money and every fiat currency is becoming worth less in purchasing power.
I am not sure why Wikipedia says that debasement is used particularly in connection with gold and silver. While these metals have a long history of serving as money, the major governments of the world have changed all of that and most money used today is paper money with no backing. So just as the kings debased money by clipping coins, today the central banks of the world debase our money via money printing (or the modern version of creating digits on a computer).
Although the term devaluation was generally used with fixed exchange rates (which we don't have any more), I really don't think there is anything wrong with this term to describe monetary inflation. When you "devalue" something, you are reducing the value of it. This perfectly describes monetary inflation as far as I'm concerned. The Federal Reserve or some other central bank creates new money out of thin air. This reduces the value of the money that we already have. It really is that simple.