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.
An index is a formula for measuring changes in a basket of stocks against a base date and value. An example of an average would be the famous Dow Jones Industrial Average, consisting of 30 blue chip stocks - that is, the stocks that most consistently return value to shareholders.