This article should be split into multiple articles accessible from a disambiguation page.

See Also Index, Washington, United States.

An index (pl. indices, sometimes indexes) is a pointer (literally - note that the index finger is the one which points, or indicates) that takes you to information.

In publishing

Main article: Index (publishing)

In publishing, indices are found at the back of books. They complement the contents page because they give access to information alphabetically.

In information technology

In computer science, an index is usually used for expressing an nth element. Indices are usually expressed as integers.

When talking about databases, indexing is a technique used by most current database management systems to speed up particular kinds of queries (usually by internally generating and storing redundant information to more quickly locate table entries).

In mathematics

In mathematics, an index is a superscript or subscript to a symbol. Superscript indices are often, but not always, used to indicate powers. Subscript indices are usually used to label a set or sequence of variables. See also index set.

The index of a subgroup is the number of its left cosets (which is equal to the number of its right cosets).

The index of a Fredholm operator is the dimension of its kernel minus the dimension of its cokernel.

The index of a real quadratic form Q is defined (but not always consistently) as p − q where Q can be written as a difference of p squared linear terms and qsquared linear terms.

In economics and finance

In economics and finance an index (for example a price index, a stockmarket index) is a benchmark of activity, performance or any evolution in general.

Consumer price indexes (an inflation measurement,) or also a country GDP index (an economic growth measurement) can be used, among other things to adjust salaries, bonds interest rates, tax thresholds...

Also, some investment funds (index funds manage their portfolio so that their evolution always mirror (tracking) the evolution of a stockmarket index.

In religion and in political ideologies

In Roman Catholicism the Index is the Index librorum prohibitorum created in 1559, the list of books that obedient Catholics were forbidden to read.

This meaning has been extended to book censorship by some political regimes.