Definition of '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 explains 'Currency Risk'
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 in the value of the Canadian dollar against the U.S. dollar. So, if you realize a 15% return in your Canadian stocks but the Canadian dollar depreciates 15% against the U.S. dollar, this will amount to no gain at all.
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.