An index is the map to a book: the gateway to the author’s ideas.

The Origins and meanings of “Index”

“Index” is derived form the identical Latin word which originally meant “that which points out”. The Latin noun was derived from the stem of the verb dicare, which meant literally “to show”, and the prefix in-, used to indicate the direction from a point outside to one within a limited distance. The verb indicare means “to make known, point out, reveal, declare, give essential information”

From large Latin dictionaries, we find that “index” also came to mean any kind of indicator, sign, token, or marker; a person who reveals or points out; the title slip of a scroll, and hence the title of a book; a summary or digest of a book or its table of contents; a list or catalog of books and their authors; and an inscription or caption. Many, but not all of these shades of meaning have been preserved until our time, and others have been added.

In ancient Roman times, an index was the title slips attached to papyrus scrolls on which the titles of the works and authors were written so that each scroll could be easily identified on storage shelves. Scrolls had neither page nor leaf numbers, nor line counts.

With the invention of the printing press, the first indexes began to be compiled. Indexes, in the modern sense, now give the exact locations of names and subjects in a book, which was not possible before the age of printing.

The alphabetical listings of names, subjects and words were referred to by the Latin terms index nominum, index rerum, and index verborum, up until the end of the 19th century. Source: Hans H. Wellisch, Indexing from A to Z.

The Oxford English Dictionary lists index (1398) as the “forefinger, pointer”; and as a piece of material that serves as a pointer (1594). The first use of the verb form of index (1720) was “to furnish (a book etc.) with an index”; and in 1761, “to enter (a word, name, etc.) with an index”. Derivations from the root index were: indexical (1828); indexer (1856); indexed (1872), indexing (1887); indexible (1951); indexation (1960)

The Oxford English Dictionary also lists: index-hunting (1699); index-hunter (1751); index-learning (1728); index-rakers (1867) and index pips (1899). (Source: Hans H. Wellisch, Indexing from A to Z. (pages 159-170))

Definitions of “Index”

Hans H. Wellisch defines an index as “an alphabetically or otherwise ordered arrangement of entries, different from the order of the material in the indexed document, and designed to enable its users to locate information in it.”


Nancy C. Mulvany offers the following: “[an index] provides a gateway to idea s and information. An index, whether it appears in the back of a book or on a CD-ROM, is a knowledge structure. Access to information is the added value that the indexer brings to the material.” Source: Nancy C. Mulvany, Indexing of Books.


The Chicago Manual of Style says “An index, a highly organized, detailed counterpart to a table of contents and other navigational aids, is also insurance, in searchable texts, against fruitless queries and unintended results”. A good index gathers all the key terms and subjects (grouping many of the former under the conceptual and thematic umbrella of the latter), sorts them alphabetically, provides cross-references to and from related terms, and includes specific page numbers or other locators. This painstaking intellectual labour serves readers of any book-length text, whether it is published on paper or online.” Source:The Chicago Manual of Style, 16th edition p. 812


International Standard ISO 999 – Information and documentation (1996)
An index is an ”ordered arrangement of entries… designed to enable users to locate information in a document or specific documents in a collection”. The ISO standard provides  guidelines for the content, organization and presentation of indexes, and covers the choice and form of headings, subheadings used in index entries.


Wikipedia. An index is a list of words or phrases (‘headings’) and associated pointers (‘locators’) to where useful material relating to that heading can be found in a document. In a back-of-the book-index the headings include names of people, places and events, and concepts selected by the indexer as being relevant and of interest to a possible reader of the book. The pointers are typically page numbers, paragraph numbers or section numbers


The Penguin Encyclopedia explains indexing as: “the compiling of systemic guides to the location of words, names and concepts in books and other publications. An index consists of a list of entries, each of which comprises a heading together with any qualifying phrase and/or subheadings, and at least one page reference or cross-reference. Individual judgment and sensitivity are essential to produce an index that is effective and a pleasure to read.”


Characteristics of an Index

  • The value of an index lies in how it is organized. It is an intricate network of interrelationships of information.
  • An index anticipates the reader’s viewpoint by providing entries that are worded and structured so as to be useful to those who are less familiar with the topic than the author, thereby giving readers quick and efficient access to the text.
  • An index is the map to the ideas and information in a book.
  • While readers can use the table of contents to get an overview of what a document contains, a good quality index guides readers to specific pieces of information. Indexes need to accommodate the needs of different readers, whether general, students, researchers or scholars. If the index entries are specific and concise, then the index will be a very effective “finding” tool. A good index increases book sales.

The Function of an Index

  • An Index discriminates between information on a subject, versus passing information on a subject.
  • An index excludes information that offers nothing significant value to potential index users.
  • An index analyzes concepts to produce a series of headings and sub-headings with page locators.
  • An index indicates relationship between concepts.
  • An Index groups together subject information that is scattered throughout the book.
  • An index anticipates the reader by directing the user to find information under related headings from cross-references.
  • An index arranges entries into a systematic and helpful order.

(adapted from Indexing Books by Nancy Mulvany)

What an Index is NOT

  • An index is not a concordance. a list of words that appear in a document.  A concordance lacks analysis, synthesis and structure. It is quite simply a list of words with a list of undifferentiated page numbers, in alphabetical order, without subheadings, cross-references, etc.
  •  An index is not an elaborate version of the table of contents. Nor is an index simply an outline of the book.
  •  An index is a separate and distinct document that has been written, not generated. An index is creative, authored work recognized by copyright registration, which enables readers to quickly and efficiently locate information within a book.

Some Quotations

Stephen Leacock: “A really good index will in most cases itself give the information wanted.”

John Ruskin: It is easy enough to make an index, as it is to make a broom of odds and ends, as rough as oat straw; but to make an index tied up tight, and that will seep well into the corners, isn’t so easy.”

Shakespeares Troilus and Cressida, I, III, 343:

And in such indexes (although small pricks To their subsequent volumes) there is seen The baby figure of the giant mass Of things to come at large.