The relative strength index, or RSI, is an oscillator that measures momentum and is used to forecast the future direction of the foreign exchange market. Day traders and scalpers, for example, can change the default parameters of the relative strength index (RSI) to monitor the market for only minutes at a time in order to determine the optimal points at which to enter and exit positions. Measuring momentum in the foreign exchange market can be useful for traders looking to develop a trading strategy that is appropriate for current market conditions.