Floridaâs tract of coral reefs has the honor of being the third-largest barrier reef ecosystem in the world. However, it could soon be a thing of the past, as the acidification of the oceanâs water is dissolving it faster than it can rebuild.
index (plural indexes or indices) 1  An alphabetical listing of items and their location. The index of a book lists words or expressions and the pages of the book upon which they are to be found. 2  The index finger; the forefinger. 3  A movable finger on a gauge, scale, etc.
Loading the player... An index is a statistical means of calculating a change in an economy or market. The index is typically a weighted average representative sample of the market. For instance, the consumer price index is a basket of goods and services that is used to represent what a typical consumer will purchase during a given time period. Changes in the price of this basket of goods lets economist know if prices increased or decreased during that time period.