Index

Look up index in Wiktionary, the free dictionary.

An index is an indirect shortcut derived from and pointing into a greater volume of values, data, information or knowledge. Index may refer to:

Business

Index Corporation, a Japanese video game developer
INDEX, a market research fair in Lucknow, India
Index fund, a collective investment scheme
Stock market index, a statistical average of prices of selected securities

Publishing

Bibliographic index, a regularly updated print periodical publication that lists articles, books, and/or other information items, usually within a particular discipline
Citation index
Index (publishing), a detailed list, usually arranged alphabetically, of the specific information in a publication
Index (typography), a (rare today) punctuation mark
Index cards in a rolodex, an old library card catalog or other organizational purpose, usually but not always 3" x 5", early and mid-20th century technologies for maintaining list of information, and in the card catalog also useful for cross-referencing information
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 (translates loosely from Latin as : "Banned Book List")
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
Index Magazine, a New York City-based publication for art and culture
Index on Censorship, a publishing organization that campaigns for freedom of expression, produces a quarterly magazine of the same name
index.hu, a Hungarian-language news and community portal
Indexed (cartoon), a Web cartoon by Jessica Hagy
The Index, the student newspaper of Kalamazoo College
The Index, an 1860s European propaganda journal created by Henry Hotze to support the Confederate States of America during the American Civil War or, a European informational journal supporting the rebellion against the United States of America during the War Between the States.
The Index, an American freethought weekly paper published 1869-1886 by Benjamin Franklin Underwood
Thumb index, a round cut-out in the pages of a publication
Truman State University Index, the weekly student newspaper of Truman State University

Sciences

Index (statistics), a concept in statistics, research design and social sciences
- A scale (social sciences), a more advanced type of an index

Biological sciences

Diversity index – a quantitative measure that increases when the number of types (distinct groups) into which a set of entities (a population) has been classified increases, and obtains its maximum value for a given number of types when all types are represented proportional to their number within the set of entities

Computer sciences

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

A number or other symbol that indicates the location of a variable in an indexed family or set
A numerical value attached to a mathematical object, such as those listed here under Algebra and Analysis
The index of summation i is used to calculate a sum

Algebra

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, 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 − q, where Q can be written as a difference of p squared linear terms and q squared linear terms.
The index of a matrix is the least integer k ≥ 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 the map $x^a \mapsto \frac{v^a(x)}{\sqrt{\sum_b(v^b(x))^2}}$ , taking points near the zero into the unit sphere111.

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, Arkansas, a community in the United States
Index:, a Danish nonprofit organization which promotes Design for Life
The Index, an item on a halo megastructure in the Halo series of video games
The Index (Dubai), a skyscraper in Dubai
INDEX was the pre-launch name for the Reimei satellite