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

Keep scrolling for more

Other Words from index

Verb

indexer noun

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
See More
Recent Examples on the Web: Noun The last 10, newly added to this year’s index, were identified as important centers in parts of the country otherwise overlooked. Daniel Wolfe, Quartz, "These cities are standing up for reproductive rights in the age of Trump," 5 Nov. 2019 The Russell 2000 index of smaller-company stocks lost 10.40 points, or 0.7 percent, to 1,562.45. BostonGlobe.com, "Stocks slip as new US-China trade jitters arise - The Boston Globe," 1 Nov. 2019 The Russell 2000 index of smaller company stocks fell 0.6%. Damian J. Troise, USA TODAY, "Stocks fall as the Fed's interest rate decision looms; General Electric among big winners," 30 Oct. 2019 As recently as a year ago, The Conference Board’s consumer confidence index hit an 18-year high of 137.9. NBC News, "Consumer confidence falls for third straight month, as trade war continues," 29 Oct. 2019 The Golden Gophers’ schedule has been quite favorable: Their strength of schedule is ranked 81st in the country in Jeff Sagarin’s index. Rainer Sabin, Detroit Free Press, "Big Ten football predictions: Week 9 schedule stuffed with tantalizing matchups," 25 Oct. 2019 September was the sector’s worst month since the tail end of the Great Recession in 2009, according to the Institute for Supply Management’s manufacturing index. Mike Rogoway, oregonlive, "Oregon Insight: A ‘manufacturing recession’?," 13 Oct. 2019 The Russell 2000 index of small capitalization stocks, typically viewed as closely tied to the health of the American domestic economy, rose 1.8 percent. New York Times, "Trump Reaches ‘Phase 1’ Deal With China and Delays Planned Tariffs," 11 Oct. 2019 The Shanghai Composite index added 0.3% while the Nikkei 225 rose 0.9%. Charles Riley, CNN, "Investors revel in trade and Brexit optimism," 11 Oct. 2019 Recent Examples on the Web: Verb Conversely, it under-indexed in mid-sized cities such as Salt Lake City. Pamela Mcclintock, The Hollywood Reporter, "'Joker' Box Office Bonanza: How the Pic Overcame a "Hard" R-Rating and Security Worries," 7 Oct. 2019 The Obama administration's proposal would have indexed the level to wage growth and adjusted it every three years. CBS News, "Trump administration weakens plan to expand overtime pay," 24 Sep. 2019 Websites on the Dark Web are not accessible via traditional web browsers and cannot be searched, or indexed, by Google and other search engines. Graham Kates, CBS News, "8chan struggles to stay online after links to mass shootings," 6 Aug. 2019 And though Google stopped indexing the 8chan homepage back in 2015, taking some wind out of its sails, the site has still managed to become a go-to for hate speech of all sorts and, of late, mass shooters spreading their extremist propaganda. Lily Hay Newman, WIRED, "Cloudflare Ditches 8chan. What Happens Now?," 5 Aug. 2019 Some in the financial industry have suggested guidelines, such as spending 4% of your assets each year, but that indexes spending to the ups and downs of the stock market and not to the needs of retirees, who risk out-living their assets. Allison Schrager, Quartz, "It’s time to get over how much we hate annuities," 3 June 2019 Why then would index funds or ETFs be any different than any other fund type or security in that respect? People love attaching a narrative to ups and downs of the markets. Ben Carlson, Fortune, "Yes, Passive Investing Has Exploded. But Here’s Why Fears of a Bubble are Overblown," 14 Sep. 2019 Since the new $400,000 threshold is not indexed while the $132,900 current-law wage ceiling rises annually with wage growth, the gap would shrink over time, such that by 2048 all earnings would be taxed by Social Security. Andrew G. Biggs, National Review, "How the Democrats’ Social Security Plan Could Finance a Tax Cut," 15 Aug. 2019 The capital gains rate itself is tied to the taxpayer’s tax bracket, which is indexed to inflation. Michael Hiltzik, Los Angeles Times, "Column: Incredibly, GOP senators are demanding billions more in tax cuts for the rich," 30 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.

See More

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

Keep scrolling for more

Learn More about index

Statistics for index

Last Updated

12 Nov 2019

Time Traveler for index

The first known use of index was in 1561

See more words from the same year

Keep scrolling for more

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
How to pronounce index (audio)

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.

Keep scrolling for more

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

Keep scrolling for more

More from Merriam-Webster on index

Thesaurus: All synonyms and antonyms for index

Rhyming Dictionary: Words that rhyme with 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

What made you want to look up index? Please tell us where you read or heard it (including the quote, if possible).

WORD OF THE DAY

the exactly right word or phrasing

Get Word of the Day daily email!

Test Your Vocabulary

Pass the Little Ribbons: A Pasta Word Quiz

  • rotelle pasta
  • Match the pasta to its meaning in English: Rotelle
Spell It

Can you spell these 10 commonly misspelled words?

TAKE THE QUIZ
Dictionary Devil

Test Your Knowledge - and learn some interesting things along the way.

TAKE THE QUIZ
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!