Trading glossaryReviewed 16 July 2026
Definition
The relative strength index is a bounded momentum oscillator that compares the magnitude of recent upward and downward price changes over a chosen lookback.
In market context
RSI values are often interpreted using upper and lower zones, but an instrument can remain in an extreme zone while a strong trend continues. Analysts also examine changes in momentum or divergence from price, both of which remain subjective and can fail. The indicator uses historical data and depends on timeframe and settings, so it should not be treated as proof that a reversal is due.
Source
Use the primary source for fuller regulatory or market context.