Index is an alphabetical list of topics and subjects that appears at the end of many books. It refers to all the important ideas or names mentioned in a book and lists the pages where they can be found. The table of contents lists chapter headings and appears at the beginning of a book.
The most common kind of index lists—in alphabetical order—the topics and the page or pages on which they appear:
Adam, 195 Diamond, 502 Emerald, 409 Gem, 111, 213, 409
An analytical index groups many individual subtopics under major subject headings. For example, the following list shows that the book contains information on gems in general and on specific gems, such as diamonds and emeralds:
Adam, 195 Gem, 111, 213, 409 Diamond, 502 Emerald, 409
Many indexes, such as those to magazines or newspapers, fill large volumes. They list articles by author, title, and subject. Some libraries have card indexes, or card catalogs, that list all their books, either on paper cards or an electronic database. Many encyclopedias have indexes large enough to fill whole volumes.
The print version of The World Book Encyclopedia uses two indexing systems. In Volumes 1 through 21, cross-references direct the reader to information (see Cross-reference). For example, a reader who looks up Air brake finds a cross-reference to Brake. In addition, a comprehensive index in Volume 22, the Research Guide/Index, provides access to specialized information of a detailed nature. It refers to volume and page numbers and to the title and subtitle of the article. A reader who looks up air brake in the index finds such entries as:
Brake (Air brakes) B:562 Railroad (Rolling stock) R:107 Westinghouse, George W:242
