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The use of this word in computing is odd. "Index" can be used as a singular to mean a particular key; a subset of keys can be referred to collectively as "indices"; then the collection of ALL keys for particular data set is an "Index" !

e.g. If Array() is an array:

Array(2) - the number 2 is an index

{2,3,4} - a set of indices in Array()

Array(n) - the position n is an Index!

I guess the first example above really should be labelled an "Index Key". To me a "key" is alphanumeric, whilst an "index" is numeric.


Index has two meanings in computing: (1) lookup table, and (4) or (5) lookup key, ID number. (I don't see much of a semantic difference between 4 and 5, as arrays are just special hashtables.) The word is overloaded, but I don't find it too confusing. Other words are much worse, take sanction that can mean something or its opposite.


I am wondering if anyone could clear this for the use of the word index, us as used in US Dollar Index and Trade Weighted US dollar Index, to wheather they are capitalized or not. Talk page on Wikipedia Enlil Ninlil 05:09, 13 August 2007 (UTC)

It should not be capitalized except when part of a proper noun, or when used as a heading. The US dollar index is just a common noun, so no capitalization unless it’s a heading. —Stephen 11:30, 13 August 2007 (UTC)


Would that be "indexes" or "indices"? -- 10:35, 9 June 2009 (UTC)

For the word taken as a whole, either form is acceptable, the former being the Anglicised plural whilst the latter is the etymologically-consistent Latinate plural. The OED’s entry for “index, n. also gives index’s as a plural in use in the seventeenth century, with a single supporting quotation from 1699 (Richard Bentley’s A dissertation upon the epistles of Phalaris). It further notes that for two of its eleven senses, the only plural in use is indices (the eighth and ninth, viz. a mathematical sense synonymous with exponent and a technical–scientific sense meaning “a number or formula expressing some property, form, ratio, etc.”, as well as their derived subsenses); for its remaining senses, it states that indices is the norm, except in the case of its fifth sense (viz. a book’s index — as well as its dervied subsenses), in which sense “indexes is usual”. I hope that answers your question.  (u):Raifʻhār (t):Doremítzwr﴿ 12:23, 9 June 2009 (UTC)


Index vs Table of Contents[edit]

I think the translation to Spanish, Basque and probably also other languages is incorrect. Índice in Spanish means "Table of contents". Index in Spanish would be something like "Glosario", although there is no specific word for it.