Index Styles

Indexers usually ask our new clients whether they have preferences for index style. Some clients have no preference and ask indexers to choose appropriate index styles for the project in-hand. We’re happy to use our professional judgment and make decisions.

Jump to: Unrealized Assumptions | House Style Guides | Indexable Material | Multiple Indexes | Heading Styles | Alphabetization | Indented v. Run-on | Subheadings | Cross-References | Page References | File Format | For More Info

Unrealized Assumptions

There are times, however, when indexes are submitted at the end of a project and the index delivered looks different than a publisher expected. With an index in hand that looks different, and a print date looming, some people suddenly discover that they do have distinct style preferences. Preferences which until now they thought were index style rules, rather than design options.

House Style Guides

Many large publishers have house style guides for indexes. Perhaps the most familiar example is Chapter 17 of The Chicago Manual of Style from the University of Chicago Press. Although this text is a style guide, it often presents more than one acceptable option for a given style issue. For that reason, even if a client asks me to “follow Chicago”, we still have style decisions to make.

Some publishers who don’t have a house style guide simply use an index that they like as a sample of what they want the finished index to look like.

Indexable Material

Many works include valuable information in their prefaces, notes, tables, and appendices, yet some publishers want only the main body of their texts to be indexed.

Unless publishers exclude these sections from their indexes, indexers read and look for indexable material in these sections in addition to the main body of the work.

Multiple Indexes

There are times when indexes have several indexes, separating subjects, from places, and names. For most books one index is sufficient, and the majority of users appreciate searching through only one index for the topics of interest to them.

Indented vs. Run-on

There are two main ways of arranging sub-headings on the page: indented and run-on. Click here to see samples of indented and run-on styles.

In indented indexes, each subheading has its own line and is indented. Most indexers use the run-on style only upon request because the majority of users say that indented indexes are easier to browse.

In run-on indexes, subheadings immediately follow each other by a semicolon and a space. Some people prefer this style because main headings and subheadings are easier to read as phrases, and are less choppy and cryptic than reading indented indexes. The run-on index format can save space for extremely long indexes.

Heading Styles

There are many decisions to make about formatting headings. The most common questions are:

  • Do you want only proper nouns capitalized?
  • Do you want sub-headings initial capped?
  • Do you want main headings to have initial caps?
  • Do you want main headings in all uppercase?
  • Would you like main headings in boldface, with cross-references not bolded?

Click here to see samples of heading styles.


Many publishers ask indexers to limit the index to only two or three levels of headings. More than three levels can be challenging for users to navigate.

In run-on indexes it is best to only have two levels of headings: a main heading and its associated subheadings.

Click here to see samples of subheading levels.

Page References

The biggest decision about page references is whether to conflate (aka elide or compress) the page numbers. Click here to see samples of page reference styles.

The Chicago Manual of Style gives two accepted options for conflating page references.

Another consideration for page references is how they’ll be separated from the entries. The most common format is to use a comma between the entry and pages. Other common options are colons, dashes, or just a couple spaces.


There are so many options that even The Chicago Manual of Style allows many acceptable formats for placement and formatting of cross-references. Click here to see samples of cross-reference styles.

  • Do you prefer to see cross-references at the beginning of an entry or at the end?
  • Do you want them run-in style or indented?
  • Do you want the See capitalized?
  • Do you want the cross-references in parentheses: (see Topic) ?
  • What punctuation do you expect to see before and after the cross-references?


There are two basic alphabetization styles: word-by-word and letter-by-letter. They differ in their treatment of spaces, numbers, and symbols. Click here to see samples of alphabetization styles.

The alphabetization style won’t make major differences in most texts. However, in the places where it does make a difference, users are thrown off by alphabetization that differs from what they expect.

In word-by-word style spaces are evaluated, so we sort letters up to the end of the first word and then stop. If two or more entries begin with the same word, the second words are sorted next.

In letter-by-letter alphabetization, spaces and other characters are ignored during alphabetizing, and words are sorted as if they are run together. (Dictionaries and phone books are sorted letter-by-letter – ever have trouble finding words or names in those?)

I sort word-by-word unless specifically asked not to because it comes naturally to most people. Michael Brackney (winner of the 2011 H.W. Wilson Award for Excellence in Indexing) created an interesting experiment in the 1990s and others have tried it since. He asked asked 35 non-indexers to sort a series of words in alphabetical order. Their instructions were “sort these terms in whatever order would be most helpful for you”. Brackney’s findings are the same as my own experiment with the same words: word-by-word sorting is favored 6:1.

Sorting of numbers and symbols also needs to be considered:

  • Do you want a section at the beginning of your index for numbers and symbols?
  • Would you prefer that numbers are alphabetized as if they’re spelled out? This means a heading for “410″ would be in the “F” section of the index.
  • Would you like symbols to be ignored when they are part of a word? Should a heading for “.sig” be in the “S” section, the “D” section (for “dot sig”), or in a section for symbols?
  • Would you like symbols to be spelled out by their names? Would a heading for “*” be in the “A” section under “asterisks (*)”.

File Format

Professional indexers can provide indexes in just about any format that publishers need: RTF, DAT, Microsoft Word, WordPerfect, PageMaker, you name it.

Our indexing software allows us to code indexes using whatever typesetting codes you require, even if it’s a coding system unique to your publishing house.

For More Info

For more information on index styles, see The Chicago Manual of Style.

If you want a more in-depth discussion of index styles and indexing techniques, I think Nancy Mulvany’s Indexing Books is the best introductory source.