An index is an ‘ordered arrangement of entries … designed to enable users to locate information in a document or specific documents in a collection’ (ISO 999, 1996). A document may be a book, periodical, film, website or any other information source.
Indexes are essential to almost any non-fiction book. They are often the first point of reference for the reader, and will be the most efficient route to finding specific information in the book. Books without indexes can be frustrating for the user, and information in the text can easily be missed.
The skill of indexing lies in analysing the document, identifying indexable terms and concepts, and creating appropriate headings. The indexer needs to be able to anticipate the needs of the user in finding suitable entry points. These may vary between different document types, such as legal or medical texts, academic journals, books for the general reader, or school textbooks.
Professional indexers use specialised software to automate the mechanical aspects of the job, but the intellectual task of selecting appropriate terms for index entries, and deciding what is significant information in a text, can only be done by a human indexer. Indexing has a long history, but the foundation of the Society of Indexers in 1957 signalled the beginning of the era of the professional indexer.