Index

{{for|Wikipedia’s index|Wikipedia:Index|selfref=y}} {{wiktionary|Index|index|indexes|indice|indices}} '''Index''' ({{plural form}}: '''indexes''' or '''indices''') most commonly refers to: * Index (publishing), an organized list of information in a publication * Web indexing, Internet indexing * An index, a key in an associative array Index may also refer to: {{tocright}} ==Arts, entertainment, and media== ===Fictional entities=== * Index (''A Certain Magical Index''), a character in the light novel series ''A Certain Magical Index'' * The Index, an item on the Halo Array in the ''Halo'' video game series

===Periodicals and news portals=== * ''Index Magazine'', a publication for art and culture * Index.hr, a Croatian online newspaper * index.hu, a Hungarian-language news and community portal * ''The Index'' (Kalamazoo College), a student newspaper * ''The Index'', an 1860s European propaganda journal created by Henry Hotze to support the Confederate States of America * ''Truman State University Index'', a student newspaper * ''The Index: A Weekly Paper Devoted to Free Religion'' (1870–1886), the semi-official periodical of the Free Religious Association

===Other arts, entertainment and media=== * The Index (band) * ''Indexed'', a Web cartoon by Jessica Hagy * ''Index'', album by Ana Mena

== Business enterprises and events == * Index (retailer), a former UK catalogue retailer * INDEX, a market research fair in Lucknow, India * Index Corporation, a Japanese video game developer

==Finance== * Index fund, a collective investment scheme * Stock market index, a statistical average of prices of selected securities

==Places in the United States== * Index, Arkansas, an unincorporated community * Index, Kentucky, an unincorporated community * Index, Missouri, a ghost town * Index, New York, a hamlet in Hartwick and Otsego, New York * Index, Virginia, an unincorporated community * Index, Washington, a town * Index, West Virginia, an unincorporated community

==Publishing and library studies== * Index (typography), a hand- or fist-shaped punctuation mark * Bibliographic index, a regularly updated publication that lists articles, books, or other information items * Citation index * The ''Index'', colloquial name for the ''List of Media Harmful to Youth and Adolescents'' (Germany) * Index card, used for recording and storing small amounts of data * ''Index Librorum Prohibitorum'', a list of publications which the Catholic Church censored * Index on Censorship, a publishing organization that campaigns for freedom of expression, or its magazine of the same name * Subject indexing, describing the content of a document by keywords * Thumb index, a round cut-out in the pages of a publication

==Science, technology, and mathematics== ===Computer science=== * Index (typography), a character in Unicode, its code is 132 * Index, the dataset maintained by search engine indexing * Array index, an integer pointer into an array data structure * BitTorrent index, a list of .torrent files available for searches * Database index, a data structure that improves the speed of data retrieval * Index mapping of raw data for an array * Index register, a processor register used for modifying operand addresses during the run of a program * Indexed color, in computer imagery * Indexed Sequential Access Method (ISAM), used for indexing data for fast retrieval * Lookup table, a data structure used to store precomputed information * Site map, or site index, a list of pages of a web site accessible to crawlers or users * Web server directory index, a default or index web page in a directory on a web server, such as index.html

===Economics=== * Index (economics), a single number calculated from an array of prices and quantities ** Price index, a typical price for some good or service

===Mathematics and statistics=== * Index, the position of an element in a sequence * Index, a number or other symbol that specifies an element of an indexed family or set * Index, an element of an index set * Index, the label of a summand in Σ-notation of a summation

==== Algebra ==== * Index of a subgroup, the number of a subgroup's left cosets * Index, the degree of an ''n''th root * Index of a linear map, the dimension of the map's kernel minus the dimension of its cokernel * Index of a matrix * Index of a real quadratic form

==== Analysis ==== * Index, the winding number of an oriented closed curve on a surface relative to a point on that surface * Diversity index, a measure of distribution or variety in fields such as ecology or information science * Index of a vector field, an integer that helps to describe the behaviour of a vector field around an isolated zero

==== Number theory ==== * Index, or the discrete logarithm of a number

====Statistics==== * Index (statistics), a type of aggregate measure ** Scale (social sciences), a method of reporting data in social sciences, sometimes called an index

===Other uses in science and technology=== * Indexicality, in linguistics, the phenomenon of a sign pointing to some object in the context in which it occurs * Indexing (motion), in mechanical engineering and machining, movement to a precisely known location * Index (physical sciences), a synonym for ratio

==Other uses== * ''INDEX'', earlier name for the Reimei satellite * Index:, a Danish nonprofit organization that promotes Design for Life * The Index (Dubai), a skyscraper * Index (crater), a Moon crater * In semiotics, an unintentional and non-arbitrary sign causally related to what it indicates, for example the smoke from a fire or the footprint of an animal.

==See also== * Indexi, a Yugoslav rock band * Indexer (disambiguation) * Directory (disambiguation) * {{Look from}} * {{In title}}