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.
4. a pointer or indicator, as in a scientific instrument. 5. Also called fist, fistnote. a printed sign in the shape of a hand with extended index finger, used to point out a note or paragraph. 6. a number or formula expressing a property or ratio: index of growth; index of intelligence.