index

verb

indexed; indexing; indexes

transitive verb

1

a

: 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

indexer noun

Synonyms of index

• list
• record
• enter
• catalog
• file

Examples of index in a Sentence

This search engine has indexed hundreds of millions of websites.

indexed all the books in the library by category

Recent Examples on the Web

Recent new partners have over-indexed in the health sector after the birth of her two daughters. —Kurt Badenhausen, Sportico.com, 1 June 2026

The Nasdaq 100 and the Dow Industrials Both indexes high new highs Wednesday. —Jason Gewirtz, CNBC, 28 May 2026

The annual limits are indexed to inflation and will rise over time. —Kinsey Crowley, USA Today, 28 May 2026

These errors often don't show up in legal databases because those databases don't index village-level political geography in West Africa. —Gloria Domingos, Forbes.com, 27 May 2026

Word History

First Known Use

1720, in the meaning defined at transitive sense 1a

Phrases Containing index

• body mass index
• card index
• cephalic index
• consumer price index
• cost-of-living index
• cranial index
• cross-index
• facial index
• glycemic index
• heat index
• index card
• index case
• index finger
• index fossil
• index-linked
• index number
• index of refraction
• index patient
• misery index
• price index
• refractive index
• therapeutic index
• the retail price index
• thumb index
• viscosity index

Video

The True Story of the Backward Index

These people needed a computer

Kids Definition

index

1 of 2 noun

in·​dex ˈin-ˌdeks 

plural indexes

-ˌdek-səz

or indices -də-ˌsēz 

1

a

: a device (as the pointer on a scale) used to indicate a value or quantity

b

: something that leads a person to a particular fact or conclusion : indication

the price of goods is an index of the economy

2

: an alphabetical list in a printed work that gives with each item listed the page number where it may be found

3

plural usually indices : a mathematical figure, letter, or expression (as the exponent 3 in a³) showing a power or root of another

4

: a symbol ☞ used to direct attention

index

2 of 2 verb

1

a

: to provide with an index

index a book

b

: to list in an index

2

: to serve as an index of

indexer noun

Medical Definition

index

noun

in·​dex ˈin-ˌdeks 

plural indexes or indices -də-ˌsēz 

1

: index finger

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

3

a

: 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 juice

—The Journal 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

index

1 of 2 noun

in·​dex

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

index

2 of 2 transitive verb

: to link (as wages, rates, or investments) to an index

under the contract wages were indexed to inflation