In finance, the exchange rates (also known as the foreign-exchange rate, forex rate or FX rate) between two currencies specifies how much one currency is worth in terms of the other. It is the value of a foreign nation’s currency in terms of the home nation’s currency. For example an exchange rate of 102 Japanese yen (JPY, ¥) to the United States dollar (USD, $) means that JPY 102 is worth the same as USD 1. The foreign exchange market is one of the largest markets in the world. By some estimates, about 3.2 trillion USD worth of currency changes hands every day.

The spot exchange rate refers to the current exchange rate. The forward exchange rate refers to an exchange rate that is quoted and traded today but for delivery and payment on a specific future date.

An exchange system quotation is given by stating the number of units of "term currency" (or "price currency" or "quote currency") that can be bought in terms of 1 "unit currency" (also called "base currency"). For example, in a quotation that says the EURUSD exchange rate is 1.4320 (1.4320 USD per EUR), the term currency is USD and the base currency is EUR.