Difference Between Index and Glossary (2026) 📑

The difference between an index and a glossary is what each one gives you. An index points to where a term appears in your book. A glossary explains what that term means. Both sit in your back matter, both run alphabetically, and they do completely different jobs.

In this guide, you’ll learn:

• The one-sentence test that separates the two every time
• Where each belongs in your back matter, in the order Chicago requires
• Whether your book needs an index, a glossary, both, or neither
• Why a print index breaks in ebooks and a glossary does not
• What each one costs to produce, and how to build them yourself

Here’s the breakdown, starting with the fastest way to tell them apart.

Index vs. Glossary: The Quick Answer

An index is a navigation tool. It lists topics, names, and concepts alphabetically with the page numbers where each one is discussed. It sends you somewhere.

A glossary is a definition tool. It lists specialized terms alphabetically with a short explanation of each. It answers a question on the spot.

The one-sentence test: if the entry ends in a number, it’s an index; if it ends in a sentence, it’s a glossary.

What Is an Index in a Book?

Index — An alphabetical list of the topics, names, and concepts covered in a book, each followed by the page numbers where that subject is discussed.

An index is not a word list. A good index is a map of ideas, not a search of strings. If your book discusses inflation across four chapters without ever using the word “inflation” in three of them, a proper index still lists all four page ranges.

That distinction is what separates a real index from an automated concordance. The ANSI/NISO Z39.4 standard for indexes, updated in 2021, defines the three processes every index depends on: comprehensive design, vocabulary management, and syntax. None of them are things a find-and-replace can do.

Indexes also use structure that a glossary never needs — subentries, cross-references, and locator ranges:

Pricing, 44-51
  anchor effect in, 47
  psychological thresholds, 48-49
  vs. value framing, 50
  see also Discounting

The subentries break a long topic into findable pieces. The see also sends you sideways to a related concept. Our full walkthrough on how to write a book index covers tagging and generating one step by step, and if you’re unsure how to pluralize the word in your own front matter, see indexes or indices.

What Is a Glossary in a Book?

Glossary — An alphabetical list of specialized, technical, or invented terms used in a book, each with a short definition written for the reader who does not already know them.

A glossary exists because you had a choice mid-chapter: stop and define a term, or keep moving. Every time you chose to keep moving, you created a glossary entry.

That’s the real function. As Grammarly’s guide to glossaries puts it, a glossary covers terms that are newly introduced, uncommon, or specific to your subject — not general vocabulary. The word “glossary” itself comes from the Latin glossarium, a collection of glosses, which were the marginal notes medieval scribes wrote to explain difficult words.

A glossary entry looks like this:

Churn — The percentage of customers who cancel a subscription in a
given period. A 5% monthly churn rate means half your customer base
turns over in roughly 14 months.

No page number. No cross-reference required. Each entry is self-contained, which is exactly why glossaries survive the jump to digital formats intact.

Fiction uses glossaries too, and heavily. Epic fantasy and science fiction both invent vocabulary faster than a reader can absorb it — house names, magic systems, alien species, constructed languages. If you’re tracking invented terms across a long series, the same material that feeds your glossary should live in your series bible.

The 7 Real Differences Between an Index and a Glossary

The table above is the summary. Here’s what actually changes in your workflow.

1. Direction of travel. An index sends the reader out of the back matter and into the body of the book. A glossary keeps them in the back matter and answers them there.

2. What earns an entry. An index includes anything a reader might want to find again — including things they already understand. A glossary includes only what they might not understand. “Chapter 3” belongs in neither, but “Rome” belongs in an index and almost never in a glossary.

3. When you can write it. You can draft a glossary while you’re still writing chapter two. You cannot finish an index until the pages are final, because the page numbers don’t exist until layout is locked.

4. Who writes it. Authors write their own glossaries — nobody knows the terminology better. Indexes are routinely outsourced, because indexing is a distinct professional skill with its own certifications and societies.

5. Format dependency. A glossary is identical in hardback, paperback, PDF, and EPUB. An index has to be rebuilt or hyperlinked for every format that paginates differently.

6. Length behavior. A glossary’s length is fixed by your subject — a book about knitting has a set number of stitches worth defining. An index’s length scales with the book. Longer book, longer index, every time.

7. Reader intent. Someone using your index has already read the book, or is browsing to decide whether to. Someone using your glossary is mid-chapter and stuck.

Where Do the Index and Glossary Go in Your Book?

The glossary comes before the bibliography. The index comes after it, and it is the last element of the reference apparatus. Getting this order wrong is one of the most common back-matter mistakes in self-published nonfiction.

The Chicago Manual of Style sets the standard sequence:

1. Acknowledgments (if not in the front matter)
2. Appendix A, Appendix B, and so on
3. Chronology (if not in the front matter)
4. Abbreviations (if not in the front matter)
5. Notes
6. Glossary
7. Bibliography or Reference list
8. List of Contributors
9. Index
10. About the author

Chicago allows one variation worth knowing: the glossary can move after the notes rather than before them if terms in your glossary appear in the notes themselves. Otherwise, glossary before notes-adjacent material, bibliography before index, always.

Two rules that follow from this order:

• The bibliography always precedes the index. Reversing them is the error editors flag most often.
• The glossary is not indexed. Neither is the bibliography. Reference apparatus doesn’t index itself.

For the full sequence including epilogues, afterwords, and reader call-to-action pages, see our guide to the back matter of a book and the companion piece on what goes in the back of a book.

Does Your Book Need an Index, a Glossary, or Both?

Most nonfiction books need one or the other, and relatively few need both. Use the reader’s likely question to decide.

You need an index if:

• Your book is a reference readers will return to, not read once
• You cover many named people, places, organizations, or events
• Libraries, universities, or professional buyers are part of your market
• Reviewers in your category expect one (history, biography, business, law, medicine)

You need a glossary if:

• You use 20+ specialized terms a general reader would not know
• You’ve invented vocabulary (fantasy, science fiction, speculative nonfiction)
• Your audience spans expert and beginner readers
• You write in a field with dense jargon — finance, medicine, technology, law

You need both if: your book is a technical reference or textbook. A cybersecurity handbook needs a glossary so readers understand “lateral movement” and an index so they can find every place you discussed it.

You need neither if: you’re writing a memoir, a novel with no invented terminology, a short self-help book, or anything readers consume linearly and never search. Adding a five-page index to a 120-page motivational book signals padding, not rigor.

Genre expectations matter more than personal preference here. Before you decide, it’s worth checking how the books you’re competing with in your category handle their back matter — the same competitive read you should be doing when structuring a nonfiction book in the first place.

Why an Index Breaks in Ebooks and a Glossary Does Not

This is the difference almost nobody explains, and it’s the one that costs indie authors the most money.

A print index is built on fixed page numbers. Reflowable EPUB — the format Kindle uses for standard ebooks — has no fixed pages. Change the font size and every page break moves. Your index entry saying “Pricing, 44-51” now points at nothing.

Your options, in order of quality:

Publishers who build indexes properly for digital replace page numbers with contextual links — the section title, figure label, or footnote marker becomes the anchor text. That’s how technical publishers like O’Reilly ship functional EPUB3 indexes.

A glossary needs none of this. It’s an alphabetical list of self-contained definitions. It works identically in every format, and a light internal-anchor pass makes each term clickable from the body text. If you’re producing both print and digital editions, the practical takeaway is that your ebook formatting budget should account for index rework and can ignore the glossary entirely.

One more digital-era note: Amazon’s Kindle Create has no indexing feature at all, and its table-of-contents support is single-level. If you’re publishing a reference-style nonfiction book through KDP, plan your index outside that tool or use dedicated book formatting software.

How to Build a Glossary for Your Book

You can build a usable glossary in an afternoon if you collect terms as you write instead of hunting for them afterward.

Step 1 — Flag as you draft. Every time you use a term and think “some readers won’t know this,” mark it. A consistent marker like [[GLOSS]] makes the final sweep a single search.

Step 2 — Cut to the terms that matter. A glossary with 300 entries is a dictionary and nobody reads it. Aim for 20-150 terms. Drop anything you defined clearly in the body text on first use.

Step 3 — Write each definition for a reader who has not read your book. Two sentences maximum. No circular definitions. Never define a term using another undefined term.

Step 4 — Alphabetize strictly, and pick a sorting rule. Decide whether “de Gaulle” files under D or G, and apply it everywhere.

Step 5 — Bold the term, then the definition. Use one consistent visual pattern. Em dash, colon, or line break — pick one.

Step 6 — Cross-reference sparingly. A see also is fine. A web of them is not.

Our Pick — Chapter

Chapter drafts nonfiction books chapter by chapter, and because it keeps your full manuscript in context, it can pull your specialized terminology into a consistent glossary instead of leaving you to grep for it in a finished Word file. It also flags terms you used before you defined them — the single most common glossary error.

Best for: nonfiction authors writing jargon-heavy books who want the back matter drafted alongside the chapters Pricing: $97 one-time (nonfiction) | Fiction plans at chapter.pub/fiction-software Why we built it: 2,147+ authors and 5,000+ books later, the pattern is consistent — the back matter is what stalls a finished draft, not the chapters.

How to Build an Index for Your Book

Indexing runs on a different clock. You cannot start until your pages are final.

Step 1 — Wait for locked layout. Any text edit after indexing shifts page numbers. Index last, always.

Step 2 — Read for concepts, not words. Mark what a topic is about, not just where its label appears. This is the step software cannot do for you.

Step 3 — Build a controlled vocabulary. Pick one heading per concept and stick to it. Don’t split “remote work” and “working remotely” into two entries — pick one and cross-reference the other.

Step 4 — Add subentries once a heading exceeds five locators. A main entry with 14 undifferentiated page numbers is useless.

Step 5 — Keep locator ranges honest. “44-51” means the discussion runs across those pages. “44, 47, 51” means three separate mentions. Don’t blur them.

Step 6 — Test it. Pick ten things a reader would want to find and try to find them using only your index. Anything you can’t locate is a missing entry.

The University of Chicago Press indexing chapter is the free, authoritative reference for the mechanics. Word and InDesign both support embedded index markers, which survive minor repagination — a meaningful advantage over a standalone list you retype.

What Does an Index or Glossary Cost?

A professional index costs roughly $3.50 to $5.50 per indexable page. A glossary costs whatever your time is worth, because you write it yourself.

According to the American Society for Indexing, typical rates run $3.50-$5.50 per book page, which puts a 300-page book at roughly $1,050 to $1,650. Complexity moves the number:

ASI’s salary survey put the average rate at $3.88 per page, and indexers also quote per entry — averaging about $0.74 each. In the UK, the Society of Indexers maintains its own recommended rates and a directory of accredited indexers.

That price gap is the practical reason so many indie nonfiction books ship with a glossary and no index. A glossary costs an afternoon. A real index costs four figures, and a bad automated one is worse than none at all.

Index vs. Glossary vs. Table of Contents vs. Appendix

These four elements get confused constantly because three of them are lists and all four are navigational in some sense. They aren’t interchangeable.

A table of contents is sequential and shallow — chapters, sometimes sections. An index is alphabetical and deep, covering concepts that never appear as a heading. That’s why a long nonfiction book needs both, and why creating a table of contents for a book is a separate job from indexing.

An appendix is different in kind: it holds full documents, datasets, or forms rather than pointers or definitions. Notably, a glossary can live inside an appendix in some academic formats — but an index never can, because the index has to cover the appendix. For where each belongs relative to the others, see appendix in a book and difference between appendix and addendum.

Can the Same Term Appear in Both the Index and the Glossary?

Yes, and in a well-built book it usually does. A term that needs defining is almost always a term readers will want to find again.

The standard convention is to make the index entry point to the term’s substantive discussion in the body text, not to the glossary page. Some publishers add a bolded or italicized locator to signal “this is where the term is defined,” which is a genuinely useful touch in textbooks.

What you should not do is index the glossary itself. The glossary is reference apparatus, and indexing it produces an entry for every term in your book pointing at the same three pages.

How Long Should an Index or Glossary Be?

An index typically runs 2-5% of your book’s page count, and a glossary runs 20-150 terms regardless of book length.

For a 300-page book, that’s roughly 6-15 pages of index at standard two-column setting. Denser technical books push toward the top of that range; narrative nonfiction sits at the bottom.

A glossary doesn’t scale with page count because it scales with vocabulary. A 200-page cryptography primer may need 90 terms. A 500-page memoir may need zero. If your glossary is creeping past 150 entries, you’re probably defining words your reader already knows.

Common Mistakes to Avoid

• Putting the index before the bibliography. Chicago order is bibliography, then index. This is the single most common back-matter error in self-published nonfiction.
• Generating an index with find-and-replace. A concordance of word occurrences is not an index. It misses every concept discussed without its label and includes every trivial mention.
• Shipping print page numbers in a reflowable ebook. Dead locators look worse than no index.
• Defining terms in the glossary that you already defined in chapter one. Redundant entries make the glossary feel like filler.
• Indexing before the layout is final. Every page number shifts and you pay twice.
• Writing glossary definitions that use other undefined jargon. If your definition of “API gateway” requires knowing what “reverse proxy” means, define both or rewrite.
• Adding an index because it looks professional. A thin, careless index damages credibility more than its absence.

FAQ

What is the difference between an index and a glossary?

The difference between an index and a glossary is what each entry provides. An index lists topics with page numbers, showing where a subject is discussed. A glossary lists specialized terms with short definitions, explaining what each one means. Both sit in the back matter, alphabetically ordered.

Does a glossary come before or after an index?

A glossary comes before an index. The Chicago Manual of Style back-matter order runs appendix, notes, glossary, bibliography, list of contributors, index, author bio. The index is the last element of the reference apparatus, and the bibliography always precedes it.

Do I need both an index and a glossary in my book?

You need both only if your book is a technical reference or textbook — jargon-heavy content readers will also search repeatedly. Most nonfiction needs one or the other. Choose a glossary for specialized vocabulary and an index for books readers return to rather than read once.

Can you have a glossary in a fiction book?

Yes. Glossaries are standard in epic fantasy and science fiction, where invented terms, houses, species, and constructed languages accumulate faster than readers can absorb them. Place it in the back matter, keep entries spoiler-free, and list only terms the text does not define in context.

Is an index worth it for a self-published book?

An index is worth it if you’re selling into libraries, academic buyers, or a reference-heavy category where reviewers expect one. At $3.50-$5.50 per page, a 300-page book costs roughly $1,050-$1,650 to index professionally. For narrative nonfiction read once, skip it and invest in a glossary instead.

What is the difference between an index and a table of contents?

A table of contents lists chapters in book order and sits in the front matter. An index lists topics alphabetically with page numbers and sits at the very back. A contents page shows structure; an index shows coverage, including concepts that never appear as chapter headings.