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index

n. · v.
US //ˈɪndɛks// UK //ˈɪndɛks// in·dex
  1. 1 book listing (n.)
    B2 Upper Intermediate

    an alphabetical list at the end of a book that shows the page numbers for specific topics.

    an alphabetical list of names, subjects, or terms with references to the places where they occur, typically found at the end of a printed work.

    Example

    If you want to find the section on climate change, look it up in the index.

    Example

    The researcher spent hours cross-referencing the index to ensure every mention of the primary source was accurately cited in the bibliography.
  2. 2 statistical measure (n.)
    C1 Advanced Academic Technical Economics

    a system or number used to measure and compare changes in things like prices or wages.

    a statistical measure of change in an economy or a securities market, often expressed as a percentage of a base value.

    Example

    The consumer price index shows how much the cost of living has gone up this year.

    Example

    Economists monitor the stock market index as a proxy for investor confidence and broader macroeconomic stability.
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  1. 3 sign or indicator (n.)
    C1 Advanced Formal Literary

    a sign or measure of something else.

    a sign, token, or indication of a particular situation, quality, or state of affairs.

    Example

    The number of new houses being built is a good index of the country's wealth.

    Example

    The rapid decline in local bird populations served as a grim index of the overall health of the ecosystem.
  2. 4 computing/data (n.)
    C1 Advanced Technical Computing

    a key or number used to find a specific piece of information in a computer's memory.

    a data structure or integer used to locate and access specific elements within an array, database, or file system efficiently.

    Example

    The program failed because it tried to access an index that didn't exist in the list.

    Example

    By creating a secondary index on the customer ID column, the database administrator significantly reduced query latency for the web application.
  3. 5 math power (n.)
    C1 Advanced Technical Math

    a small raised number that shows how many times to multiply a number by itself.

    a number or symbol, often written as a superscript, indicating the power to which a quantity is to be raised.

    Example

    In the expression 10 to the power of 3, the number 3 is the index.

    Example

    Students must learn the laws of indices before they can solve complex algebraic equations involving roots and powers.
  4. 6 to create a list (v.)
    B2 Upper Intermediate

    to make an alphabetical list of the topics in a book or document.

    to record names or topics in an index; to provide a book or document with an index.

    Example

    The library is working to index all of its old newspapers so people can search them online.

    Example

    The software automatically indexes every word in the document, allowing for instantaneous full-text searching across the entire archive.

    Usage

    The verb is transitive and requires a direct object.
  5. 7 to link to an index (v.)
    C1 Advanced Technical Formal Economics

    to link wages or prices to a system so they change automatically when costs go up.

    to adjust a value, such as a salary or interest rate, automatically according to changes in a price index.

    Example

    The government decided to index pensions to inflation to help retired people.

    Example

    The union negotiated a contract where annual pay increases are indexed to the national cost-of-living adjustments.
Origin

From Latin index (“a discoverer, informer, spy; of things, an indicator, the forefinger, a title, superscription”), from indicō (“point out, show”); see indicate.

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