index

noun
in·​dex | \ ˈin-ˌdeks How to pronounce index (audio) \
plural indexes or indices\ ˈin-​də-​ˌsēz How to pronounce indices (audio) \

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

Highs head for the mid-90s and heat indexes rise to and past 100. Ian Livingston, Washington Post, "D.C.-area forecast: Temperatures rise this weekend, and it stays hot into next week," 17 Aug. 2019 The National Weather Service has issued a heat advisory from noon to 7 p.m. Saturday in Houston and surrounding cities and counties, with heat indexes ranging from 106 to 110 degrees. Jasper Scherer, Houston Chronicle, "Heat advisory in effect Saturday in Houston, surrounding area," 17 Aug. 2019 But humidity levels will be on the increase, making the heat index climb above 100 degrees in many locations. Leigh Morgan, al, "Hot, hot, hot today: Who will hit 100 degrees?," 17 Aug. 2019 There can be no outdoor practice or workouts when the heat index is more than 92 degrees, according to state guidelines. NBC News, "High school basketball player dies while working out in brutal Georgia heat," 16 Aug. 2019 The heat index hit 117 (47 Celsius) before noon Tuesday in the Mobile, Alabama, area. Jeff Martin And Jay Reeves, chicagotribune.com, "Dreadful heat, humidity invade South as misery continues," 15 Aug. 2019 The heat index soared to 121 degrees by late afternoon in Clarksdale, Miss., and to 119 degrees in West Memphis, Ark., the weather service reported. Jeff Martin, BostonGlobe.com, "Dangerous heat grips wide stretch of the South and Midwest," 12 Aug. 2019 The last time the heat index was below 100 degrees in Galveston was about 5 a.m. Thursday. Jesus Jimenez, Dallas News, "Heat index values in Galveston have not dipped below 100 degrees for more than 30 hours," 9 Aug. 2019 The heat index will be close to or slightly above 100 degrees. courant.com, "Another 90-degree day," 30 July 2019

Recent Examples on the Web: Verb

Highlights of Pete Buttigieg's economic proposal The federal minimum wage would be set at $15 an hour and would be indexed to median wage growth. Alexandria Burris, Indianapolis Star, "Pete Buttigieg would let gig-economy workers unionize, set $15 minimum wage," 26 July 2019 SmartAsset’s indexed the results to 100, with 100 indicating where Social Security would cover most of people’s needs. Judith Kohler, The Denver Post, "Want to get the most out of Social Security dollars in Colorado? Report says Custer County is the place for you.," 16 July 2019 Other commonsense changes, such as raising and indexing the retirement age and using a more accurate inflation index, would help as well. Rachel Greszler, National Review, "Taxing Inheritances Won’t Fix Social Security," 9 July 2019 The gas tax last was raised in 1990 and will be indexed to the rate of inflation in the future. Kimberly Fornek, chicagotribune.com, "Drivers, gas station owners react to first day of state fuel tax increase," 1 July 2019 By the 1970s, the number indexed a wealth of sensitive information in computer data banks, prompting major privacy legislation. Time Staff, Time, "15 Unsung Moments From American History That Historians Say You Should Know About," 28 June 2019 Today’s booklets are also easier to use, more clearly organized and indexed. Zachary Lewis, cleveland.com, "Cleveland Orchestra program book editor Eric Sellen relishes role as musical liaison," 13 June 2019 Under a national system of industry-wide salary awards, pay in many jobs, from cabin crew to funeral directors, is in effect indexed to the minimum wage. The Economist, "Australia has the world’s highest minimum wage," 20 July 2019 The state’s 19-cent-per-gallon motor fuel tax, last raised in 1990, doubled to 38 cents per gallon and will be indexed to future inflation increases. Mary Wisniewski, chicagotribune.com, "Lightfoot says she won’t raise Chicago’s gas tax," 1 July 2019

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

20 Aug 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

noun

English Language Learners Definition of index

 (Entry 1 of 2)

: an alphabetical list at the end of a book that shows the page where each thing in the list can be found
: a group of related things that are in alphabetical or numerical order
: a sign or number that shows how something is changing or performing : a number that indicates changes in the level of something (such as a stock market) when it rises or falls

index

verb

English Language Learners Definition of index (Entry 2 of 2)

: 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 How to pronounce index (audio) \
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 How to pronounce index (audio) \
plural indexes or indices\ -​də-​ˌsēz How to pronounce indices (audio) \

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

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