Currency Risk
A form of risk that arises from the change in price of one currency against another. Whenever investors or companies have assets or business operations across national borders, they face currency risk if their positions are not hedged.
Investopedia Commentary
For example if you are a U.S investor and you have stocks in Canada, the return that you will realize is affected by both the change in the price of the stocks and the change of the Canadian dollar against the U.S. dollar. Suppose that you realized a return in the stocks of 15% but if the Canadian dollar depreciated 15% against the U.S. dollar, you would realize no gain.
Academic studies of currency risk suggest - although, without absolute certainty - that investors bearing currency risk are not compensated with higher potential returns, meaning it is essentially a needless risk to bear.
Related Links
Floating And Fixed Exchange Rates
Corporate Use of Derivatives for Hedging
A Primer On The Forex Market
See also: Currency, Exchange Rate, Hedge, Transaction Exposure, Translation Exposure