n. pl. in·dex·es or in·di·ces (-dĭ-sēz′)
1. Something that serves to guide, point out, or otherwise facilitate reference, especially:
a. An alphabetized list of names, places, and subjects treated in a printed work, giving the page or pages on which each item is mentioned.
b. A thumb index.
c. A table, file, or catalog.
d. Computers A list of keywords associated with a record or document, used especially as an aid in searching for information.
2. Something that reveals or indicates; a sign: "Her face ... was a fair index to her disposition" (Samuel Butler).
3. A character (☞) used in printing to call attention to a particular paragraph or section. Also called hand.
4. An indicator or pointer, as on a scientific instrument.
a. Mathematics A number or symbol, often written as a subscript or superscript to a mathematical expression, that indicates an operation to be performed, an ordering relation, or a use of the associated expression.
b. A number derived from a formula, used to characterize a set of data.
a. A statistical value that represents the price or value of an aggregate of goods, services, wages, or other measurable quantities in comparison with a reference number for a previous period of time.
b. A number that represents the change in price or value of stocks or other securities in a particular market, sector, or asset class.
c. The stocks or other securities represented by an index.
7. Index Roman Catholic Church A list formerly published by Church authority, restricting or forbidding the reading of certain books.
tr.v. in·dexed, in·dex·ing, in·dex·es
a. To furnish with an index: index a book.
b. To enter in an index.
2. To indicate or signal.
3. To adjust through indexation.
[Middle English, forefinger, from Latin; see deik- in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2017 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
The American Heritage Dictionary Blog
Check out our blog, updated regularly, for new words and revised definitions, interesting images from the 5th edition, discussions of usage, and more.
American Heritage Dictionary Products
The American Heritage Dictionary, 5th Edition
The American Heritage Dictionary of Idioms
The American Heritage Roget's Thesaurus
Curious George's Dictionary
The American Heritage Children's Dictionary
The American Heritage Dictionary of Indo-European Roots
The American Heritage Student Grammar Dictionary
The American Heritage Desk Dictionary + Thesaurus
The American Heritage Science Dictionary
The American Heritage Dictionary of Business Terms
The American Heritage Student Dictionary
The American Heritage Essential Student Thesaurus