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English definition of “index”

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index

noun uk   /ˈɪn.deks/ ( plural indices or indexes) us  

index noun (LIST)

C1 [C] an alphabetical list, such as one printed at the back of a book showing which page a subject, name, etc. is on: Try looking up "heart disease" in the index. [C] a collection of information stored on a computer or on a set of cards, in alphabetical order: He still has all his friends' names and addresses on a card index.
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index noun (COMPARISON)

[C] a system of numbers used for comparing values of things that change according to each other or a fixed standard: the FTSE 100 Index the Dow Jones Index a wage/price index [C usually singular] something that shows how strong or common a condition or feeling is: Consumer spending is often a good index of public confidence in the economy.
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index

verb [T] uk   /ˈɪn.deks/ us  

index verb [T] (MAKE LIST)

to prepare an index for a book or collection, or arrange it in an index: Our computer indexes several thousand new records every second. The book contains a lot of information, but it's not very well indexed.

index verb [T] (COMPARE)

to change a system of numbers according to each other or a fixed standard: Living expenses will be indexed to/in line with inflation (= to take inflation into consideration).
(Definition of index from the Cambridge Advanced Learners Dictionary & Thesaurus © Cambridge University Press)
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