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'{{selfref|For the use of the word "index" in Wikipedia, see [[Wikipedia:Index (disambiguation)]]}} {{wiktionary|index}} '''Index''' may refer to: ==Business== * [[Index (retailer)]], a defunct UK catalogue retailer formerly owned by the Littlewoods group and known as ''Littlewoods Index'' * [[INDEX]], a market research fair in Lucknow, India * [[Index fund]], a collective investment scheme * [[Stock market index]], a statistical average of prices of securities ==Publishing== * [[Bibliographic index]], a regularly updated print periodical publication that lists articles, books, and/or other information items, usually within a particular discipline * [[Index (publishing)]], a detailed list, usually arranged alphabetically, of the specific information in a publication * [[Index (typography)]], a largely obsolete punctuation mark * [[Index card]]s in a rolodex or old library card catalog, early and mid 20th century technologies for maintaining such lists * Germany's List of Media Harmful to Young People, colloquially known as ''The Index'', published by the [[Bundesprüfstelle für jugendgefährdende Medien]] * ''[[Index Librorum Prohibitorum]]'', a list of publications which the Catholic Church censored * ''[[Index Magazine]]'', a New York City-based publication for art and culture * [[index.hu]], a Hungarian-language news and community portal * [[Indexed (cartoon)|''Indexed'' (cartoon)]], a Web cartoon by [[Jessica Hagy]] * ''The Index'', the student newspaper of [[Kalamazoo College]] * [[The Index (journal)|''The Index'' (journal)]], a European propaganda journal created by [[Henry Hotze]] to support the Confederate States of America during the American Civil War * [[Thumb index]], a round cut-out in the pages of a publication * ''[[Toaru Majutsu no Index]]'', a Japanese light novel, manga, and anime series * ''[[Truman State University Index]]'', the weekly student newspaper ==Sciences== * A [[scale (social sciences)]] ===Biological sciences=== *[[Diversity index]] – a quantitative measure that increases when the number of types into which a set of entities has been classified increases, and obtains its maximum value for a given number of types when all types are represented by the same number of entities ===Computer science=== * [[Lookup table]], a data structure, usually an array or associative array, often used to replace a runtime computation with a simpler array indexing operation * Array index, an integer pointer (into an [[array data structure]]) that identifies an element of the array * A ''key'' in an [[associative array]] * [[Database index]], a data structure that improves the speed of data retrieval operations on a database table * [[Index mapping]], mapping of raw data, used directly as in array index, for an array * [[Index register]], a processor register used for modifying operand addresses during the run of a program * The dataset maintained by [[search engine indexing]] * [[Indexed color]] * [[Indexed Sequential Access Method]] (ISAM), a method for indexing data for fast retrieval * [[Subject indexing]], describing the content of a document by keywords * [[Web indexing]] (Internet indexing) * [[Site map]], a list of pages of a web site accessible to crawlers or users * [[Webserver directory index]], a default or index web page in a directory on a web server, such as index.html * [[BitTorrent index]], a list of .torrent files available for searches ===Economics=== * [[Index (economics)]], a single number calculated from an array of prices and quantities ** [[Price index]], a typical price for some good or service ===Geography=== * [[Index, New York]], a hamlet in the County and Town of [[Otsego, New York]], United States * [[Index, Washington]], a town in Snohomish County, Washington, United States *[[Index, West Virginia]] ===Library and information science=== * [[Back-of-the-book index]] * [[Bibliographic index]], a regularly updated print periodical publication that lists articles, books, and/or other information items, * [[Index (publishing)]], a detailed list, usually arranged alphabetically, of the specific information in a publication * [[Subject indexing]], describing the content of a document by keywords ===Linguistics=== * [[Indexicality]], the variation of meaning of an utterance according to certain features of the context in which it is uttered ===Mathematics=== <!--Source: Borowski and Borwein, ''Collins Dictionary of Mathematics'', 2nd ed, HarperCollins Publishers, London, 1989, 2002. p 277.--> * A number or other symbol that indicates the location of a variable in an [[Indexed family|indexed family or set]] such as a list or array of numbers or other mathematical objects, usually written as a [[subscript]] to the variable; e.g. in the list <math>\lbrace x_1, x_2, x_3, x_4\rbrace</math>, the number <math>3</math> is the ''index'' of the third element, <math>x_3</math>. * A numerical value attached to a mathematical object, such as those listed here under [[#Algebra|Algebra]] and [[#Analysis|Analysis]] ==== Algebra ==== * [[Exponent]] * The degree of an [[nth root]] * The [[index of a subgroup]] is the number of a subgroup's left cosets (which is equal to the number of its right cosets). * The index of a [[linear map#Index|linear map]], is the dimension of the map's kernel minus the dimension of its cokernel. * The index of a real [[quadratic form]] ''Q'' is defined (but not always consistently) as ''p'' &minus; ''q'' where ''Q'' can be written as a difference of ''p'' squared linear terms and ''q'' squared linear terms. * The index of a [[Matrix (mathematics)|matrix]] is the least integer ''k'' &ge; 0 such that rank(''A''^''k''+1) = rank(''A''^''k''). ==== Analysis ==== * The [[winding number]] of an oriented closed curve on a surface relative to a point on that surface; loosely speaking, the number of times the curve goes around the point counter-clockwise * The [[index of a vector field]] ''v'' at an isolated zero is the [[degree of a continuous mapping|degree]] of the map <math>x^a \mapsto \frac{v^a(x)}{\sqrt{\sum_b(v^b(x))^2}}</math>, taking points near the zero into the unit sphere. ==Technologies== ===Mechanics=== * [[Indexing (motion)]], a kind of motion in many areas of mechanical engineering and machining ===Optics=== * [[Refractive index]], a measure for optical properties of transparent materials. ==Other usages== * [[Index finger]], the second digit of a human hand *[[Index:]] a Denmark nonprofit organization which promotes Design for Life * [[Index Ventures]], a venture capital investment firm based in Switzerland * The Index, an item on a [[Halo (megastructure)|halo megastructure]] in the ''Halo'' series of video games * [[The Index (Dubai)]], a skyscraper in Dubai *[[FamilySearch Indexing]] including indexing the US 1940 Census *[[A Certain Magical Index|Index Librorum Prohibitorum]], a character from the Japanese light novel, anime and manga ''A Certain Magical Index''. "Index" may refer either to the character, or the series. <!--Interwikies--> {{disambiguation}}'