From Wikipedia, the free encyclopedia
  (Redirected from Index (information technology))
Jump to: navigation, search
For the use of the word "index" in Wikipedia, see Index (disambiguation)

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


  • Index (retailer), a defunct UK catalogue retailer formerly owned by the Littlewoods group and known as Littlewoods Index
  • 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 securities



Biological sciences[edit]

  • 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[edit]


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


Library and information science[edit]


  • Indexicality, the variation of meaning of an utterance according to certain features of the context in which it is uttered


  • A number or other symbol that indicates the location of a variable in an 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 \lbrace x_1, x_2, x_3, x_4\rbrace, the number 3 is the index of the third element, x_3.
  • 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, e.g.:
\sum_{i \mathop =3}^5 i = 3+4+5 = 12.


  • 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 pq, 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 {{{1}}}.


  • 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 sphere.



  • Indexing (motion), a kind of motion in many areas of mechanical engineering and machining


Other usages[edit]