index

noun
in·​dex | \ ˈin-ˌdeks \
plural indexes or indices\ ˈin-​də-​ˌsēz \

Definition of index

 (Entry 1 of 2)

1 : 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
b : a list of publicly traded companies and their stock prices
c : a bibliographical analysis of groups of publications that is usually published periodically
2a : 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
3a : 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
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 {latex}\sqrt[3]{5}{/latex} to indicate the cube root of 5
5 : a character ☞ used to direct attention to a note or paragraph

called also fist

6 : a list of restricted or prohibited material specifically, capitalized : a formerly published list of books the reading of which was prohibited or restricted for Roman Catholics by the church authorities

index

verb
indexed; indexing; indexes

Definition of index (Entry 2 of 2)

transitive verb

1a : 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

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Other Words from index

Verb

indexer noun

Synonyms for index

Synonyms: Noun

hand, indicator, needle, pointer

Synonyms: Verb

catalog (or catalogue), enroll (also enrol), enter, inscribe, list, put down, record, register, schedule, slate

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Examples of index in a Sentence

Noun

Look up the recipe for potato soup in the index. Potato soup is listed under “soup” in the index. The card catalog is an index to the materials in the library. the index on a scale

Verb

This search engine has indexed hundreds of millions of Web sites. indexed all the books in the library by category
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Recent Examples on the Web: Noun

Energy stocks rebounded alongside oil prices, helping major indexes trim their early slide. Mike Bird, WSJ, "U.S. Stocks Inch Higher in Wobbly Start to the Year," 2 Jan. 2019 That means the funds passively track an index, like the S&P 500. Ellen Sheng, Marie Claire, "A Beginner's Guide to Investing," 2 Jan. 2019 While in late 2017 and early 2018, US stocks rallied, the markets have since become rockier, and major indexes have given back their post-tax bill gains. Emily Stewart, Vox, "What the Republican tax bill did — and didn’t — do, one year later," 18 Dec. 2018 The three major indexes all fell more than 5 percent between Wednesday and Thursday, and tech shares like Apple, Alphabet and Netflix failed to rebound after posting steep losses. Recode Staff, Recode, "Recode Daily: Silicon Valley may have a Saudi Arabia problem," 12 Oct. 2018 The dial has orange indices (the hour indicators) with a bezel cut from nautical teak, the wood found on the decks of the finest boats. Matt Hranek, Condé Nast Traveler, "Time and Place: Hublot in Brooklyn," 26 Sep. 2018 Hedge funds this year have outperformed the S. & P.’s United States bond index, which has lost 1.17 percent. James B. Stewart, New York Times, "Hedge Funds Should Be Thriving Right Now. They Aren’t.," 12 July 2018 After news emerged that Xiaomi would be included in the Hang Seng index, alongside the likes of Tencent and China Mobile, its shares popped by more than 13%. David Meyer, Fortune, "Xiaomi Surge, Trade War and Tesla, Uber and Lime: CEO Daily for July 10, 2018," 10 July 2018 Led by big technology and small-company stocks, all of the major U.S. stock indexes finished the April-June quarter with gains. Adam Shell, USA TODAY, "401(k) investors: What are the risks and rewards for the rest of 2018," 2 July 2018

Recent Examples on the Web: Verb

Backups and software updates affected, too The flaw, indexed as CVE-2018-12020, means that decades' worth of email messages many people relied on for sensitive business or security matters may have in fact been spoofs. Dan Goodin, Ars Technica, "Decades-old PGP bug allowed hackers to spoof just about anyone’s signature," 14 June 2018 But about 30 years after publishing the first Systema Naturae, Linnaeus came up withanother way to index his information: by putting all of the organisms and minerals on smaller, thicker pieces of paper. Jonathan Schifman, Popular Mechanics, "How the Humble Index Card Foresaw the Internet," 11 Feb. 2016 The bug, formally indexed as CVE-2018-7602, exists within multiple subsystems of Drupal 7.x and 8.x. Dan Goodin, Ars Technica, "Drupal users take cover—code-execution bug is being actively exploited [updated]," 25 Apr. 2018 These numbers were indexed to the number of Peloton customers observed in Q1 2017. Rani Molla, Recode, "Peloton now has more U.S. customers than SoulCycle, new data suggests," 3 Dec. 2018 At its core, Google indexes the entire web — some hundreds of billions of pages — using programs called web crawlers. Ryan Nakashima, The Seattle Times, "AP EXPLAINS: How Google search results work," 28 Aug. 2018 Indexing capital gains without indexing interest payments and depreciation would not make the tax system neutral with respect to inflation, which is a sensible goal. Alan S. Blinder, WSJ, "Index Capital Gains, but Not Without Congress’s Consent," 1 Aug. 2018 Of course, Google already has all of that information indexed, whether it’s puppy breeds, restaurant menus, clothing inventory, or foreign languages. Lauren Goode, WIRED, "Lens, Google's Visual Search Tool, Gets Its Most Significant Update Yet," 8 May 2018 At President Reagan’s behest, Congress in the 1980s indexed much of the federal tax code for inflation. Kimberley A. Strassel, WSJ, "Trump Alone Can Cut Taxes," 12 July 2018

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.

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First Known Use of index

Noun

1561, in the meaning defined at sense 3a

Verb

1720, in the meaning defined at transitive sense 1a

History and Etymology for index

Noun

Latin indic-, index, from indicare to indicate

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Statistics for index

Last Updated

8 Jan 2019

Look-up Popularity

Time Traveler for index

The first known use of index was in 1561

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More Definitions for index

index

noun

Financial Definition of 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.

Source: Investing Answers

index

verb

English Language Learners Definition of index

: 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

noun
in·​dex | \ ˈin-ˌdeks \
plural indexes or indices\ ˈin-​də-​ˌsēz \

Kids Definition of index

 (Entry 1 of 2)

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 sense 1 the index on a scale
3 : sign entry 1 sense 3, indication Prices are an index of business conditions.

index

verb
indexed; indexing

Kids Definition of index (Entry 2 of 2)

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

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index

noun
in·​dex | \ ˈin-ˌdeks \
plural indexes or indices\ -​də-​ˌsēz \

Medical Definition of index

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
3a : 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 juiceJournal 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

index

noun
in·​dex

Legal Definition of index

 (Entry 1 of 2)

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

Legal Definition of index (Entry 2 of 2)

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

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More from Merriam-Webster on index

Rhyming Dictionary: Words that rhyme with index

Thesaurus: All synonyms and antonyms for index

Spanish Central: Translation of index

Nglish: Translation of index for Spanish Speakers

Britannica English: Translation of index for Arabic Speakers

Britannica.com: Encyclopedia article about index

Comments on index

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