What is an Index?

An index is not a concordance, a list of all the words that appear in a document. A concordance lacks analysis and synthesis. It is simply a list of words. [emphasis added]**

The U.S. National Information Standards Organization (NISO)*, in their 2021 Criteria for Indexes, defines an index simply as, “a systematic guide to facilitate retrieval of content.”

According to NISO:

Index as Enabler

The indexer’s job is to present useful and efficient access points to information in the text.**

In short, indexers methodically analyze the text to be indexed and use their judgment, based on indexing expertise and (general) knowledge of the subject material at hand, to create a useful tool for readers, enabling them to efficiently find the information they seek.

*ANSI/NISO Z39.4 Criteria for Indexes (Baltimore, MD: National Information Standards Organization), p.3-4.

**Nancy Mulvany. Indexing Books (Chicago: University of Chicago Press, 2005), p.10; 86.