Index

in·dex   (ĭn'děks')    n.   pl. in·dex·es or in·di·ces (-dĭ-sēz') Something that serves to guide, point out, or otherwise facilitate reference, especially: An alphabetized list of names, places, and subjects treated in a printed work, giving the page or pages on which each item is mentioned. A thumb index. A table, file, or catalog. Computer Science A list of keywords associated with a record or document, used especially as an aid in searching for information. Mathematics A number or symbol, often written as a subscript or superscript to a mathematical expression, that indicates an operation to be performed, an ordering relation, or a use of the associated expression. A number derived from a formula, used to characterize a set of data. Something that reveals or indicates; a sign: "Her face . . . was a fair index to her disposition" (Samuel Butler). A character () used in printing to call attention to a particular paragraph or section. Also called fist, hand. An indicator or pointer, as on a scientific instrument. Mathematics A number or symbol, often written as a subscript or superscript to a mathematical expression, that indicates an operation to be performed, an ordering relation, or a use of the associated expression. A number derived from a formula, used to characterize a set of data. A number that represents the change in price or value of an aggregate of goods, services, wages, or other measurable quantity in comparison with a reference number for a previous period of time. Index Roman Catholic Church A list formerly published by Church authority, restricting or forbidding the reading of certain books. tr.v.   in·dexed, in·dex·ing, in·dex·es To furnish with an index: index a book. To enter in an index. To indicate or signal. To adjust through indexation. [Middle English, forefinger, from Latin; see deik- in Indo-European roots.] in'dex'er n.

Index

A statistical measure of change in an economy or a securities market. In the case of financial markets, an index is essentially an imaginary portfolio of securities representing a particular market or a portion of it. Each index has its own calculation methodology and is usually expressed in terms of a change from a base value. Thus, the percentage changes is more important that the actually numeric value. For example, knowing that a stock exchange is at, say, 5,000 doesn't tell you much. However, knowing that the index has risen 30% over the last year to 5,000 gives a much better demonstration of performance.

The plural of index can be spelled either indexes or indices.

Investopedia Commentary

The Standard &amp Poor's 500 is one of the world's best known indexes, and is the most commonly used benchmark for the stock market.

Technically, you can't actually invest in an index. Rather, you invest in a security such as an index fund or ETF that attempts to track an index as closely as possible.

Related Links

Index Investing Tutorial
A Market By Any Other Name
Indexes: The Good, The Bad And The Ugly

See also: DAX, DJIA, DJTA, DJUA, E-mini, ETF, FTSE, Index Arbitrage, Index Fund, Index Futures, Index Hugger, Index Option, Passive Management, S&P 500, Wilshire 5000 Index

Also spelled: Index, Indices, Indice

index

The relative value of a variable in comparison with itself on a different date. Many security price indicators such as the Standard & Poor's series and the New York Stock Exchange series are constructed as indexes. Also called stock index. See also base period.

Main Entry: in·dex
Function: noun
: a numerical measure or indicator (as of inflation or economic performance) —see also CONSUMER PRICE INDEX

Main Entry: in·dex
Pronunciation: 'in-"deks
Function: noun
Inflected Form: plural in·dex·es or in·di·ces /-d&-"sEz/
1 : FOREFINGER
2 : a list(as of bibliographical information or citations to a body of literature) arranged usually in alphabetical order of some specified datum (as author, subject, or keyword) <Index Medicus of theU.S. National Library of Medicine>
3 a : a ratio or other number derived from a series of observations and used as an indicator or measure (as of a condition, property, orphenomenon) indexes of the urine, the blood, and the gastric juice —Journal of the American Medical Association> b : the ratio of onedimension of a thing (as an anatomical structure) to another dimension —see CEPHALIC INDEX, CRANIAL INDEX

index in·dex (ĭn'děks')
n. pl. in·dex·es or in·di·ces (-dĭ-sēz')

1. A guide, standard, indicator, symbol, or number indicating the relation of one part or thing to another in respect to size, capacity, or function.

2. A core or mold used to record or maintain the relative position of a tooth or teeth to one another or to a cast.

3. A guide, usually made of plaster, used to reposition teeth, casts, or parts.

4. The index finger.

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in'dex' v.

index of refraction   A measure of the extent to which a substance slows down light waves passing through it. The index of refraction of a substance is equal to the ratio of the velocity of light in a vacuum to its speed in that substance. Its value determines the extent to which light is refracted when entering or leaving the substance.

index
(Plural "indices" or "indexes")
1. A number used to select an element of a list, vector, array or other sequence. Such indices are nearly always non-negative integers but see associative array.
2. See inverted index. [Other kinds?]
3. A search engine.
4. A subject index.
[The Jargon File]
(1997-04-09)