index

UK/ˈɪndɛks/US/ˈɪndɛks/

nounB25 meanings Common in everyday speech and writing · #5,818 of 15,258mostly written

Other forms: indexed, indexing, indexes

An index is the alphabetical list at the back of a book telling you which page each topic is on. You look up volcanoes, it says 214, you turn to 214.

The word reaches a long way from there. A figure that tracks something over time is an index — a price index, a share index like the FTSE. In a database an index is what makes searching fast, and in programming the index is an item's position in a list, counted from zero in most languages. Your index finger is the pointing finger. The plural splits by meaning: books have indexes, mathematics and statistics have indices. As a verb, to index a book is to make the list for it.

Definitions of index

1nounindexAn alphabetical list of topics with the pages where each one is found.B2~5%
“Look it up in the index at the back.”
2nounnumberA number showing how something changes over time.C1~89%
“The cost of living index rose again this month.”
3nouncomputingIn computing, a structure that makes searching fast, or an item's position in a list.C1~2%
“The query is slow because that column has no index.”
4nounfingerThe finger next to the thumb, used for pointing.B2~2%
“She tapped the map with her index finger.”
5verbbookTo make an index for a book, or to record something in an index.B2~2%
“It took her a month to index the whole volume.”

Shares are an estimate: a language model read 21 sentences found in the wild and placed 20 of them on a sense (1 were unclear) — a count of our sample, not a measurement of English.

index is a list that points you somewhere.

Where it comes from

Latin index meant a pointer — an informer, a sign, and, of the hand, the forefinger. It came from indicō, "to point out, to show", which also stands behind indicate, and further back a Proto-Indo-European root *deyḱ- for showing. An index at the back of a book is still a finger: it points you at the page.

Proto-Indo-European
*deyḱ-
Latin
index
English, today
index

Built from

indicō · Latin — point out, show

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

Etymology from Wiktionary, CC BY-SA

Practised in A Man Called Ove, Computing & Code, Libraries & Museums

First appears in chapter 1 of A Man Called Ove.

Practise this word

index in the wild

The index is a price-weighted index; stocks with the highest price per share have the highest weighting in the index.
Dow Jones Industrial Average
However, in the long run, the index has performed in line with the broader S&P 500.
Dow Jones Industrial Average
In total, there was approximately $13 trillion in assets tracking the index as of December 31, 2024.
S&P 500
The index is associated with many ticker symbols, including ^GSPC,.
S&P 500
The index does not take into account several factors, such as the net wealth per capita or the relative quality of goods in a country.
Human Development Index

1 / 5

From Wikipedia, CC BY-SA 4.0. These sentences were written by other people about their own subjects; they are here to show the word at work, not as anybody’s opinion.

Related words

the indicō family

indicate indication index

index — used about once every 1,595 pages · #5,818 · point at the bar for the others

Definitions of index

1nounindexAn alphabetical list of topics with the pages where each one is found.B2~5%

“Look it up in the index at the back.”

2nounnumberA number showing how something changes over time.C1~89%

“The cost of living index rose again this month.”

3nouncomputingIn computing, a structure that makes searching fast, or an item's position in a list.C1~2%

“The query is slow because that column has no index.”

4nounfingerThe finger next to the thumb, used for pointing.B2~2%

“She tapped the map with her index finger.”

5verbbookTo make an index for a book, or to record something in an index.B2~2%

“It took her a month to index the whole volume.”

Shares are an estimate: a language model read 21 sentences found in the wild and placed 20 of them on a sense (1 were unclear) — a count of our sample, not a measurement of English.

index is a list that points you somewhere.