The reader cannot tell which of the many references contains the information sought. A good index, however, will not have more than five page numbers for one heading. Where there would be more than five, the heading is broken down, enabling users to narrow their search. Indexes, however, contain subheadings that represent the various aspects of the main heading. The search is narrowed by the increasing amount of detail given at each heading level.
Readers can find, at a glance, the aspect of the concept they are after.
It is better to index ideas as main headings so that readers can find them in the alphabetical list than to have them buried in a sea of subheadings. Indexes are synonym rich Computer-generated lists are limited to the words actually used in the document, and cannot give you synonyms of those words. But with an index, one concept can appear as, or under, several different headings. This is crucial, because different people may attach different terms to the same concept. Cross-references are used to send the reader from one concept to another, related, concept or to a synonym.