1

index

play
noun in·dex \ ˈin-ˌdeks \
Updated on: 26 Jul 2017

Definition of index

plural indexes or indices play \ˈin-də-ˌsēz\
1 a :a device (such as the pointer on a scale or the gnomon of a sundial) that serves to indicate a value or quantity
b :something (such as a physical feature or a mode of expression) that leads one to a particular fact or conclusion :indication
2 :a list (as of bibliographical information or citations to a body of literature) arranged usually in alphabetical order of some specified datum (such as author, subject, or keyword): such as
a :a list of items (such as topics or names) treated in a printed work that gives for each item the page number where it may be found
c :a bibliographical analysis of groups of publications that is usually published periodically
d :a list of publicly traded companies and their stock prices
3 :a list of restricted or prohibited material; specificallycapitalized :a formerly published list of books the reading of which was prohibited or restricted for Roman Catholics by the church authorities
4 plural usually indices :a number or symbol or expression (such as an exponent) associated with another to indicate a mathematical operation to be performed or to indicate use or position in an arrangement
  • 3 is the index of the expression ∛5 to indicate the cube root of 5
5 :a character ☞ used to direct attention to a note or paragraph called also fist
6 a :a number (such as a ratio) derived from a series of observations and used as an indicator or measure; specifically :index number
b :the ratio of one dimension of a thing (such as an anatomical structure) to another dimension

Examples of index in a Sentence

  1. Look up the recipe for potato soup in the index.

  2. Potato soup is listed under soup in the index.

  3. The card catalog is an index to the materials in the library.

  4. the index on a scale

Recent Examples of index from the Web

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'index.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Origin and Etymology of index

Latin indic-, index, from indicare to indicate

index Synonyms

Synonyms
hand, pointer, indicator, needle
Related Words
dial, face, gauge (also gage)

2

index

verb

Definition of index

transitive verb
1 a :to provide with an index
b :to list in an index
  • all persons and places mentioned are carefully indexed
2 :to serve as an index of
3 :to regulate (wages, prices, interest rates, etc.) by indexation
intransitive verb
:to index something

indexer

noun

Examples of index in a Sentence

  1. This search engine has indexed hundreds of millions of Web sites.

  2. indexed all the books in the library by category

Recent Examples of index from the Web

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'index.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of index

1720

index Synonyms


Financial Definition of INDEX

index

What It Is

An index is a statistical aggregate that measures change. In finance, they usually refer to measures of stock market performance or economic performance.

How It Works

Let's say we want to measure the stock price performance of the widget industry. There are currently four public companies that make widgets in the United States: Company A, Company B, Company C, and Company D. In the year 2000, when we started caring about the seedling U.S. widget industry, the four companies' stock prices were as follows:

Company A     $10
Company B     $8
Company C     $12
Company D     $25

Total $55

To create an index, we simply set the total ($55) in the year 2000 equal to 100 and measure any future periods against that total. For example, let's assume that in 2001 the stock prices were:

Company A     $4
Company B     $38
Company C     $12
Company D     $24

Total $78

Because $78 is 41.82% higher than the 2000 base, the index is now at 141.82. Every day, month, year, or other period, the index can be recalculated based on current stock prices.

Note that this index is weighted by stock price (i.e., the larger the stock price, the more influence it has on the index). Indexes can be weighted by shares outstanding, market capitalization, or any other factors the indexer chooses. When new companies go public or existing companies founder, the indexer may add or delete companies from the index or "reweight" the index to accommodate stock splits or other factors.

Why It Matters

In finance, the most significant numbers in any given day's news are usually market indices. The Dow Jones Industrial Average is probably the best-known and most widely followed financial index in the world. It consists of 30 The definition of index on InvestingAnswersof the largest publicly traded firms in the United States. The S&P 500 Index is also very common, comprising over 70% of the total market cap of all stocks traded in the U.S. The Nasdaq Composite is a broad market index that encompasses about 4,000 issues traded on the Nasdaq National Market -- virtually every firm that trades on the exchange.

Indices are also used to gauge activity in an economy. Perhaps the best known economic index in the United States is the CPI, or Consumer Price Index, which measures inflation.



INDEX Defined for English Language Learners

index

verb

Definition of index for English Language Learners

  • : to provide an index for (something, such as a book)

  • : to list or include (something) in an index

  • : to link wages, benefits, etc., to a measurement of changes in the price of goods and services so that they increase at the same rate


INDEX Defined for Kids

1

index

play
noun in·dex \ ˈin-ˌdeks \

Definition of index for Students

plural indexes or indices \ˈin-də-ˌsēz\
1 :a list of names or topics (as in a book) given in alphabetical order and showing where each is to be found
2 :pointer 1
  • the index on a scale
3 :1sign 3, indication
  • Prices are an index of business conditions.

2

index

verb

Definition of index for Students

indexed; indexing
1 :to provide (as a book) with an index
2 :to list in an index
  • The topics are indexed.

Medical Dictionary

index

play
noun in·dex \ ˈin-ˌdeks \

medical Definition of index

plural indexes or indices play \-də-ˌsēz\
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 the United States 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, or phenomenon)
  • physiochemical indexes of the urine, the blood, and the gastric juice
  • Journal of the American Medical Association
b :the ratio of one dimension of a thing (as an anatomical structure) to another dimension — see cephalic index, cranial index

Law Dictionary

1

index

noun in·dex

legal Definition of index

:a numerical measure or indicator (as of inflation or economic performance) — see also consumer price index

2

index

transitive verb

legal Definition of index

:to link (as wages, rates, or investments) to an index
  • under the contract wages were indexed to inflation


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