# index

Pronunciation: say "IN-deks" /ˈɪndɛks/

## Noun

1. An alphabetical listing of items along with the location where each one can be found.
   - Simple: An alphabetical list that shows where to find things, like topics in a book.
   - _She scanned the index for any mention of the author's earlier works._
   - _A well-made index lets readers locate a single fact in seconds._
2. A number expressing a property or ratio, such as a coefficient that measures some characteristic.
   - Simple: A number that measures a property or compares two amounts.
   - _The refractive index of water is about 1.33._
   - _Diamond has a very high refractive index, which helps it sparkle._
3. A single figure calculated from a set of prices or quantities, used to track how they change overall.
   - Simple: A single number that shows how a group of prices or amounts changes over time.
   - _The consumer price index showed inflation slowing in the third quarter._
   - _Economists revised the index after new wage data arrived._
5. The forefinger; the finger beside the thumb, commonly used for pointing.
   - Simple: The finger next to the thumb, used for pointing.
   - _The surgeon flexed her index to test the nerve's response._
   - _Guitar teachers often tell beginners to press the string with the tip of the index, not the flat pad._
6. A data structure that speeds up operations on a database table, especially searches.
   - Simple: A helper structure in a database that makes searching a table much faster.
   - _Creating an index on the email column sped up user lookups dramatically._
   - _Every index consumes extra disk space and must be updated on each write._
7. An integer or key that marks the position of an item within an array, list, or similar data structure.
   - Simple: A number that shows where a piece of data sits in a list or table.
   - _She accessed the element by passing its index to the function._
   - _An out-of-range index threw an exception at runtime._
8. A sign or indication that reveals the nature, existence, or degree of something.
   - Simple: A sign that shows something exists or tells you what it is like.
   - _Her trembling hands were an index of how nervous she felt._
   - _The condition of a city's parks is an index of civic pride._
12. A movable pointer on a gauge, dial, or scale that indicates a reading.
   - Simple: A pointer that moves across a dial or scale to show a measurement.
   - _The brass index swept across the dial as the temperature climbed._
   - _Calibrating the instrument meant aligning the index with the zero mark._
13. A small raised number showing the power to which a quantity is raised; an exponent.
   - Simple: A small raised number that tells how many times to multiply a number by itself.
   - _In x⁴, the index 4 shows that four x's are multiplied together._
   - _She forgot to lower the index when differentiating the term._

## Verb

4. To compile an alphabetical guide to the contents of a text, showing where each topic appears.
   - Simple: To make an alphabetical list that shows where to find topics in a book.
   - _A professional was hired to index the dense legal volume._
   - _She carefully indexed every name mentioned in the diaries._
9. To adjust a value for inflation by linking it to a price index, keeping its real level constant.
   - Simple: To adjust an amount of money so it keeps the same real value as prices rise.
   - _Lawmakers voted to index benefits so they track rising prices._
   - _Their rent is indexed to inflation each January._
10. To access a value in a data container by referring to its index.
   - Simple: To get a value from a list or table by using its position number.
   - _Developers index the array with a loop variable to read each element._
   - _The function indexes the dictionary by key to return the stored value._
11. To measure something by reference to an associated value.
   - Simple: To measure something by comparing it to a related value.
   - _Sociologists often index living standards by access to clean water._
   - _The report indexes biodiversity by the number of species present._
14. To serve as an indexical sign for some situation or state of affairs; to indicate it.
   - Simple: To be a sign of something or point to it.
   - _In sociolinguistics, certain pronunciations index a speaker's regional background._
   - _Dropping the g in 'running' can index a relaxed, casual tone._

## Noun

15. An introductory section or prologue that indicates what is to follow in a work. *(obsolete)*
   - Simple: A short opening part that tells you what is coming in a book or play.

## Other meanings

- (verb) To use a mechanism to move an object step by step to a precise location.
- (verb) To make an inventory of something; to take stock of what is on hand.
- (noun) A typographic mark shaped like a hand with an extended finger, used to direct a reader's attention to a particular note or passage.
- (noun) In group theory, the number of distinct cosets of a subgroup within a group.
- (noun) An expression whose referent changes according to the context of use; 'today's newspaper,' for instance, points to a different paper each day.

## Origin

From the Latin index ("a discoverer, informer, indicator, forefinger, or title"), formed from in- and dīcō ("to say, indicate"); related to indicō ("to point out, show") and to indicate.

Source: DictionaryAI, https://dictionaryai.com/define/index (written from Wiktionary data, CC BY-SA 4.0: https://creativecommons.org/licenses/by-sa/4.0/).