The term "stock market index" refers to a statistical measure that provides insight into the performance of a group or segment of stocks within a specific market. Synonyms for this phrase include "market index," "stock index," "equity index," or simply "index." Other similar terms that can be used to describe stock market indices include "benchmark," "composite," "average," and "indicator." Some specific examples of popular market indices include the S&P 500, NASDAQ Composite, and Dow Jones Industrial Average. Despite their different names, all of these indices serve the same purpose of measuring the overall health and performance of a particular stock market.