Definition: Exchange rate
The price of one currency in terms of another. Most commonly, exchange rates are expressed as the number of units of domestic currency that will purchase one unit of foreign currency (e.g. units of currency per U.S. dollar). An exchange rate may also be defined as the inverse: the number of units of foreign currency that one unit of domestic currency will purchase.
International Monetary Fund (IMF), "Online glossary of selected financial terms" (as per March 15th, 2008), International Monetary Fund, Washington D.C., 2008