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Indices vs. Indexes

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When words have more than one variant, choosing between them can be difficult. Often, there is no hard and fast rule, so writers must rely on context to determine the best word to use. Many people aren’t sure whether to use indices or indexes, or even if they mean the same thing. This article will shed some light on these confusing terms.

In this post, I will show you the difference between indices and indexes. I will use each of the two words in example sentences that will display them in context.

Origin:

The word indices is the plural of index which originated from late Middle English: from Latin index, indic- ‘forefinger, informer, sign’, from in- ‘towards’ + a second element related to dicere ‘say’ or dicare ‘make known’; compare with indicate. The original sense ‘index finger’ (with which one points), came to mean ‘pointer’ (late 16th century), and figuratively something that serves to point to a fact or conclusion; hence a list of topics in a book (‘pointing’ to their location).

Index as noun:

The word index is used as a noun which means (in a book or set of books) an alphabetical list of names, subjects, etc. with reference to the pages on which they are mentioned.

Clear cross references supplemented by a thorough index.

Index also means a sign or measure of something.

Exam results may serve as an index of the teacher's effectiveness.

A pointer on an instrument, showing a quantity, a position on a scale, etc. is also known as index.

The index jumped up the dial.

Index as verb:

Index is used as a verb in English language too where it means to record (names, subjects, etc.) in an index.

The list indexes theses under regional headings.

Index also means to link the value of (prices, wages, or other payments) automatically to the value of a price index.

The Supreme Soviet passed legislation indexing wages to prices.

Use of indexes:

The word indexes is the non-technical plural form of index. For those writers adhering to AP Style, you should use this spelling and this spelling alone, as AP prefers indexes over indices.

Examples:

The number of market indexes now exceeds the number of U.S. stocks. Traditional ones such as the S&P 500 are collections of securities weighted by market value, and index funds mimic them as a low-cost way to deliver the market’s performance. –Bloomberg BusinessWeek

A quick tour around the world’s stock indexes will reveal the extent of Mr. Market’s New Year rethink. [Wall Street Journal]

This year is looking tougher, though. Asian stock indexes are off to a rocky start with increasing concerns over rising inflation and other macroeconomic conditions. [New York Times]

Indexes in idle mode: Stock rally fed by Europe deal slows [USA Today]

Use of indices:

Indices is a more technical version of the same plural noun. This version more closely approximates the original Latin form. It is common in many mathematical and technical contexts.

Examples:

David Blitzer, managing director and chairman of the index committee at S&P Dow Jones Indices, said the low stock of existing homes for sale — currently about 3.8 months worth of supply at current sales rates — is bolstering the price increases across the board. –CNBC

Despite the fact we have major challenges of poverty, in all the indices of community engagement we are thriving. [Guardian]

Of the 45 indices that make up the MSCI World Index, 36 recorded declines of more than 20 per cent. [Irish Times]

For the average direct investor or trader, the market and the indices that represent it are almost completely irrelevant. [Sydney Morning Herald]

Indices or indexes:

Indexes and indices are two versions of a plural noun that means an indicator or a list of names. Indexes is also a present tense verb, but indices cannot be used that way. Indexes is probably the better choice for formal writing not related to mathematics. Indices is especially common in technical and formal writing. AP Style requires the spelling indexes. Let style and flow be your guide with these two words.

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"Indices vs. Indexes." Grammar.com. STANDS4 LLC, 2017. Web. 25 Nov. 2017. <http://www.grammar.com/indices_vs._indexes>.

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