The Arms index (TRIN) is a technical analysis indicator that compares advancing and declining stock issues and trading volume as an indicator of overall market sentiment. It measures the relationship between market supply and demand and is used as a predictor of future price movements in the market, primarily on an intraday basis. The Arms index seeks to provide a more dynamic explanation of overall movements in the composite value of stock exchanges, such as the NYSE or NASDAQ, by analyzing the strength and breadth of these movements.