Index

How to spell index

5 letters · 2 syllables

How to pronounce index

Say the part in capitals loudest.

What does index mean?

1. nounAn alphabetical list of names, subjects, or topics at the end of a book, with the page numbers where each appears.
2. nounA number that measures relative change or value over time, often used in economics or finance.
3. verbTo compile a reference list for, or to arrange information so it can be quickly located.

Index in a sentence

• noun

  The textbook has a detailed index that lists every topic by page.

• noun

  The consumer price index rose by two percent last quarter.

• verb

  The software can automatically index every document in the archive.

• noun

  She checked the index to find where the author discussed taxation.

• noun

  Investors tracked the stock market index throughout the trading day.

• verb

  They paid an editor to index the entire reference manual.

Where does index come from?

Language of origin: Latin

Index comes straight from Latin, where it was the noun for a pointer or forefinger, built from the verb indicare, meaning 'to point out' or 'to make known', itself from in- 'toward' and dicare 'to declare', a relative of dicere 'to say'. The Romans used index for anything that points, including the forefinger (the digitus index, literally 'the pointing finger') and an informer who points out wrongdoing. English borrowed the word in the late 1500s, first for a pointer or sign and then for the alphabetical guide at the back of a book, which 'points' the reader to the right page. From there it spread into mathematics for an exponent and into statistics and economics for a number that points to relative change. The word keeps its Latin shape almost untouched, which is why the plural 'indices' still survives beside the everyday 'indexes', and the same dicare root sits inside 'indicate' and 'dictate'.

How the word is built

• in- (toward, into)
• dex (from dicere: to point, to say)