Index (noun)

1. A list of items in a book or document, typically with their page numbers.
2. A numerical value used to indicate the level or rate of change of something.

Origin:

From middle english endex, from old french endex, from latin index ("pointer, indicator"), from indicare ("to indicat.e")

Examples:

1. The index at the back of the book lists all the names and places mentioned in the book.
2. The stock market index is a measure of the performance of the stock market as a whole.
3. He used the index to find the page he needed quickly.
4. The inflation index helps economists to measure changes in prices over time.
5. The index finger is the finger used for pointing.