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


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

Other Words from index


indexer noun

Synonyms for index

Synonyms: Noun

Synonyms: Verb

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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 websites. indexed all the books in the library by category See More
Recent Examples on the Web: Noun The gravestones of its Radicals Row read like an index to the history of the American Left. Ron Grossman, Chicago Tribune, 13 May 2022 JPMorgan economist Michael Feroli has constructed an index of economic disruption based on how much employment growth varies between individual sectors. Greg Ip, WSJ, 12 May 2022 The index of 37 meme stocks compiled by Bloomberg has reached a record low in the last few days, down 63% from its peak in January 2021. Michael Hiltzik, Los Angeles Times, 12 May 2022 Shell's shares rose 3.3% in early trading, outperforming the 1.8% rise of an index of oil and gas companies. Reuters, CNN, 5 May 2022 The SSE Composite Index also known as SSE Index is a stock market index of all stocks that are traded at the Shanghai Stock Exchange. Frank Holmes, Forbes, 2 May 2022 An Asia-Pacific equity index eked out a climb for the first time in four sessions amid a 3% jump in technology shares in Hong Kong. Vildana Hajric, Fortune, 26 Apr. 2022 For example, there are no Asian women CEOs in the Standard and Poor's 100, which is an index of the nation's largest and most valuable companies. Taylor Wilson, USA TODAY, 25 Apr. 2022 Currie says private investors are driving up the price of oil stocks, which have gone up nearly 78% in the last year, per an S&P index tracking such equities. Tim Fernholz, Quartz, 22 Apr. 2022 Recent Examples on the Web: Verb Currently, 13 states do not index their income tax brackets to inflation, mostly in the South and Mid-Atlantic regions. Adam A. Millsap, Forbes, 13 Apr. 2022 The 1940 census records were released a decade ago, but the federal government didn't transcribe and index the names. Bill Bowden, Arkansas Online, 10 Apr. 2022 Congress should ultimately index unemployment benefits nationwide, but in the short run, states must take the lead. Jonathan Ingram, WSJ, 5 Jan. 2022 The original plan was a nonstarter for too many members, but a small group of senators is working on a proposal to index the price of a select number of drugs. Lauren Fox And Phil Mattingly, CNN, 26 Oct. 2021 Republicans insisted on no change to corporate tax rates; the Biden Administration and congressional Democrats adamantly opposed proposals to index the gas tax or enact fees on electric vehicles. Susan B. Glasser, The New Yorker, 24 June 2021 In 1983, William Foege, the agency’s director at the time, advised Congress to index a portion of total health care spending and reserve it for public health. New York Times, 16 June 2021 After 2022, the order will also index the $15 minimum wage for federal contractors to inflation, so it will be automatically adjusted to reflect changes in the cost of living going forward. Fin Gómez, CBS News, 27 Apr. 2021 Another option would be to simultaneously increase the gas tax further and index it to inflation. oregonlive, 21 Apr. 2021 See More

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


1561, in the meaning defined at sense 3a


1720, in the meaning defined at transitive sense 1a

History and Etymology for index


Latin indic-, index, from indicare to indicate

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Last Updated

16 May 2022

Cite this Entry

“Index.” Dictionary, Merriam-Webster, Accessed 22 May. 2022.

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More Definitions for index


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.


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.


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



Legal Definition of index

 (Entry 1 of 2)

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


transitive verb

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

More from Merriam-Webster on index

Nglish: Translation of index for Spanish Speakers

Britannica English: Translation of index for Arabic Speakers Encyclopedia article about index


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