What is indexing?

Indexing is all about finding stuff – often information in books or journals, though it might be items in a collection or even the contents of your attic. The purpose of an index is to help the user find what they're looking for. Indexing is the process of creating such a 'finding aid' by examining the material to be indexed, identifying the significant items and concepts, devising the terms to describe these, adding appropriate cross-references, and putting them all into (usually) alphabetical order.

What makes a good index?

There is no one 'right' way to index (say) a book. But a good index will be created with the needs of the users in mind. This means, for example, including terms that the user may look for which may be different from the language used in the text. Other features of a good index include:

  • clear, easy-to-follow layout
  • no more than about 6 undifferentiated page references against a single entry
  • helpful see and see also cross-references
  • appropriate use of subheadings
  • concise but unambiguous terms
  • consistent style
  • accuracy – the right page numbers, and correct spelling, punctuation and order

Why use a professional indexer?

Professional indexers are familiar with current standards in indexing and information retrieval, and experienced in constructing indexes from the point of view of the user. They come to the material with fresh eyes and can approach the task objectively. (Incidentally, an indexer will often pick up errors missed by the author and editor – thus providing an extra layer of checking.) Indexing is not a quick process, but professional indexers use dedicated indexing software which cuts down the time taken and enables them to prepare the index in practically any style or format required by the client.

More information on commissioning indexes can be found on the Society of Indexers website. 

Isn't the author the best person to write the index?

Indexing requires a particular combination of skills. Some authors are also good indexers, and may enjoy indexing their own work. The author has the advantage of knowing the book and its subject well. If the subject is highly specialized, the author may be the only person capable of indexing it! But not all authors have the desire or aptitude to be an indexer. Even if they do, the index can benefit from being compiled by someone who is not so close to the work and can more easily put themselves in the position of the potential reader. Also, authors may underestimate just how tired of the book they will be when the time comes to index it. Even professional indexers who themselves are authors, often get a colleague to write the index for them.

More information for authors can be found on the Society of Indexers website. 

Can't the index be compiled by computer these days?

Computers cannot, by themselves, produce good indexes. They can spot words or phrases and identify page numbers. But it's still the case that good indexing requires human intellectual input. For example, a computer cannot

  • distinguish between significant treatment of a subject and mere mentions
  • distinguish between homographs (words that are spelled the same but have different meanings, e.g. file (a document) and file (a tool)
  • recognise synonyms, alternative terms or misspellings
  • identify concepts and themes not mentioned by name
  • identify where discussion of a subject begins and ends
  • recognise context

There is specialist indexing software that can help with the more repetitive tasks involved in creating, organising, sorting and formatting index entries.