If you are looking for specific information in a book, rifling through each page is inconvenient and cumbersome, especially if the book is hundreds of pages long. You certainly cannot use a Search function: this is found only in electronic devices. The solution is an index.
What Is an Index?
A book index is an alphabetized list of words and phrases showing the page numbers on which text on the subjects listed can be found. The index is typically placed at the end of a book. While not needed in novels or short books, an index is required for most textbooks, technical manuals and other books that contain factual information. An index can be as short as a page, and as long as 10 or 20 pages or more.
A good index is not merely a list of vocabulary words and page numbers. Rather it presents concepts and tasks using language that a reader can understand. For example, a book on car maintenance might include the term "lubrication" to refer to a page on oil changes. More reader-friendly index terms for the same subject would be "oil" and "grease." Task-related terms would include "Changing the oil" and "Scheduling oil changes."
The entries of an index are alphabetized into one or more columns. Each entry consists of an index term, followed by a number that can show one page (35), a range of pages (35-44) or the start of a range (35 ff.). The letter that begins a set of entries is typically used as a header for those entries. For example, you will find all entries that begin with the letter "a" under the heading "A."
Who Makes an Index?
The book's author is normally responsible for creating the index. However, publishers often use a professional indexer who can perform the task with more thoroughness and speed. They then deduct the cost of the indexer from the author's final pay.
How Is an Index Made?
Indexes are usually created after the book is laid out as a final proof. An indexer goes through each page and types potential entries and page numbers into a separate document. She then edits that document for consistency and usefulness before sending it to the publisher who typesets the index and merges it into the book for printing.