The Relative Strength Index (RSI) is a momentum oscillator used in technical analysis to measure the speed and change of price movements. It ranges from 0 to 100 and helps traders identify overbought or oversold conditions in a market. Typically, an RSI above 70 indicates that an asset may be overbought, while an RSI below 30 suggests it may be oversold. Developed by J. Welles Wilder Jr., the RSI is calculated using the average gains and losses over a specified period, usually 14 days. This indicator is widely used in conjunction with other tools to make informed trading decisions and assess market trends.