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
d
2a : a number (such as a ratio) derived from a series of observations and used as an indicator or measure specifically
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

Verb

indexer noun

Synonyms for index

Synonyms: Noun

Synonyms: Verb

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

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

Recent Examples on the Web: Noun

The University of Michigan's preliminary sentiment index edged up to 98.4 from 98.2 in June, according to data released Friday that were about in line with forecasts. With Louisville under an excessive heat warning by the National Weather Service and heat indexes reaching as high as 110 degrees this weekend, Crockett said that now is an especially important time to make others aware of the issue. Heat indexes of over 100 degrees were already recorded from Miami to Minneapolis on Friday. July and August were responsible for 22 out of the 25 highest emission months nationally between 2001 and 2018, according to Carnegie Mellon University’s power-sector carbon index. As a quick refresher, the hand signal in question is made by extending the index and pinky fingers while grasping the middle two fingers with the thumb. The peak heat indexes expected in Central Indiana haven't been seen since 2012, Ryan said. Even up north, Friday temperatures could bring a 95-degree heat index. Holding the top spot on the index is Amazon CEO and founder Jeff Bezos at $125 billion. Recent Examples on the Web: Verb That same holding indexed to inflation would be subject to a 21.4% tax rate, the research service said. Under legislation from 1990, legislators are entitled to automatically receive cost-of-living increases indexed to the federal rate of inflation. The gas tax, last raised in 1990, will be indexed to future inflation increases. Recently, Pro Publica even caught Intuit using a robots.txt file to prevent Google from indexing the free version of Turbotax, preventing many eligible users from finding it. Since interest payments are not indexed, the entire 8% interest is probably deductible—not only the 4% real interest payments. The gas tax last was raised in 1990 and would be indexed to future inflation increases. Varietiescalled guaranteed and indexed universal lifewere created later and became big sellers. New York manufacturers, meanwhile, reported modest growth in February, with a business conditions index rising to 8.8 from 3.9 the previous month. 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 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 Share index Resources for index Dictionary Entries near index Statistics for index Last Updated 23 Jul 2019 Look-up Popularity 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 of 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

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 \
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 \
plural indexes or indices\ -​də-​ˌsēz \

Medical Definition of index

1
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

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

Rhyming Dictionary: Words that rhyme with index

Thesaurus: All synonyms and antonyms for index

Spanish Central: Translation of index

Britannica English: Translation of index for Arabic Speakers

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

desideratum

something desired as essential

Get Word of the Day daily email!

What's that Smell?! Quiz

• Someone who is hircine smells like a:

Can you spell these 10 commonly misspelled words?

TAKE THE QUIZ

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!