Relative Strength Index answers a narrow question: how completely have recent closes dominated the lookback window? It does not answer whether those closes attracted broad participation.

A classroom habit

When RSI prints a new high with the market, we require a second line in the notebook: volume expanding, flat, or contracting across the same swing. Expanding volume with rising RSI is a different conversation from rising RSI on a dry tape.

We use the same pairing with MACD histogram expansion. The oscillator names the acceleration; volume names whether the room filled. Separating those sentences keeps momentum from becoming a permission slip.