An index is a document that is scanned to find information. It usually spans several pages. But if you had to break an index down into its smallest part, what would that be?
An index is not like most books or documents in that it does not contain a narrative. It cannot be reduced to plot points or the components of an argument. An index doesn’t even contain proper sentences. Instead, an index is a compilation of references. Broken down, the smallest unit within an index is an entry.
An entry has two components. Basically, “what this thing is + where to find it.” Using indexing terminology, this is “main heading + locator.” Or, to add another level of specificity, “main heading + subheading + locator.” From the entry, the reader can identify what they are looking at and where to find it in the text. For example,
Foxconn, 45
semiconductors: geopolitics of, 67
The second building block is an array. I like to think of an array as containing everything that an index—and by extension the book or document—has to say about a particular subject. If you want to learn about Foxconn, you search for the Foxconn array. Want to learn about semiconductors, you search for the semiconductors array.
If there is only one mention, then a single entry can serve as a single array. But more often, there are multiple discusses throughout the book, which lead to the creation of multiple entries. Combined together, the entries create an array.
Foxconn, 45, 49, 51-52
semiconductors: fabrication techniques, 54-57; geopolitics of, 67; history of, 23-25; properties of, 34, 44
Why are entries and arrays so important? No one writes an index composed of a single entry.
But every index begins with an entry, and as the index is written, the entries and arrays accumulate. It is through knitting the entries and arrays together than an index emerges.
Step one to writing an index is to write clear, concise, and specific entries, so that “what this thing is” is clear to the reader. Step two is to combine entries into arrays which are clearly organized and easy to scan. Step three is to sort and organize the arrays—creating the structure of the index—so that the index as a whole is easy to navigate.
Each of these elements—the entry and the array—fit together, like interlocking pieces, to create a coherent whole.
A Note about Terminology
I’ve noticed that not every indexer, including books about indexing, distinguishes between entries and arrays. I’m guilty myself of using the terms interchangeably, though I try to be clear when I’m writing.
But while terminology varies, I do think that the distinction is important. Because an index is composed of hundreds or thousands of pieces of information, it helps to know what these pieces are and how they interact with each other. An index is also easier to edit and organize if these building blocks are clearly written and well thought out.
As you index, how are these building blocks fitting together? How can you be more mindful of each piece of information and how it interacts with the entries and arrays around it? Does it make a difference to think about indexing as building up from the smallest unit to the larger whole?