Glossary vs Index: What’s the Difference?

Glossary vs Index Quiz: Test Yourself

Five quick questions on glossary vs index. Pick an answer to get instant feedback.

Flip Cards: Quick Review

Hover over a card, or tap it on mobile, to see the key idea.

Students, writers and readers often stop to ask glossary vs index because both are alphabetical lists near the end of a book, and both help you find your way around. They do different jobs, though. One explains words, and the other points to pages. This guide explains the difference between a glossary and an index, shows where each one belongs, and helps you decide which your own document needs.

What is a glossary?

A glossary is a list of specialized, technical or unfamiliar words and their definitions, arranged alphabetically. It works like a small dictionary built for one book or document, so readers can check a term without leaving the text for a separate dictionary.

• A science textbook might define “photosynthesis” and “ecosystem.”
• A legal guide might explain terms such as “tort” and “plaintiff.”
• A novel with foreign words might include a glossary of those words.

Good glossary entries use short, plain-language definitions. Some terms may have more than one meaning, and the glossary can list them.

What is an index?

An index is an alphabetical list of the topics, names and terms in a work, with the page numbers where each appears. It acts as the book’s built-in search tool, taking readers straight to the right page.

• An entry such as “climate change, 45, 112” tells you which pages to read.
• “See” and “see also” notes point to related entries.
• Subentries break a big topic into smaller parts.

Because entries are alphabetical, the page numbers will probably be out of order. That is normal, since the index is arranged by topic, not by position in the book.

What is the key difference between a glossary and an index?

A glossary gives definitions, and an index gives page numbers. If you want to know what a word means, you check the glossary. If you want to find where a topic is discussed, you check the index.

Both are alphabetical, and both are useful in informational and academic texts. That shared format is why people mix them up, even though the information they provide is different.

How do they differ from a table of contents?

A table of contents lists chapters and sections in the order they appear, usually at the front of the book. An index lists topics alphabetically, usually at the back. The table of contents shows the structure, while the index lets you find specific details anywhere in the text.

Where do the glossary and the index go?

Both belong in the back matter, which is the material after the main text. One common order is appendices, endnotes, glossary, bibliography and then index, with the index as the very last item. Exact placement can vary by publisher and style guide, so follow the guidelines you have been given.

Do you need a glossary, an index or both?

It depends on the readers and the content. Many nonfiction and academic works benefit from both, since the vocabulary can be specialized and readers often want to re-find specific points. Fiction rarely needs an index, although a novel with unfamiliar words may include a glossary.

• Add a glossary if your text uses technical terms or foreign words many readers will not know.
• Add an index if readers will want to look up topics, names or ideas after reading.

Longer reference-style works often include a professional index, and many authors hire an indexer.

What about the plural of index?

Both “indexes” and “indices” are used. “Indexes” is the common choice for lists at the back of books, while “indices” is common in mathematics, science and finance. Either is understood, so pick one and stay consistent.

Glossary vs index: which word should you use?

Ask what the reader needs. Use glossary for definitions of terms. Use index for finding where something is discussed.

Compare these pairs:

• Check the glossary if you don’t know what “ecosystem” means. (A definition.)
• Check the index to find every page that mentions ecosystems. (Page numbers.)
• Use the table of contents to jump to a chapter. (Order of chapters.)

Common mix-ups about glossaries and indexes

• ✗ A glossary tells you which pages to read.
  ✓ That is an index. A glossary gives definitions.
• ✗ An index explains what words mean.
  ✓ That is a glossary. An index gives page numbers.
• ✗ The index is always at the front of the book.
  ✓ It is usually at the very end.
• ✗ A glossary and a table of contents are the same thing.
  ✓ A table of contents lists chapters in order, while a glossary defines terms alphabetically.
• ✗ Every novel needs an index.
  ✓ Fiction rarely does, though some include a glossary of unfamiliar words.

How can you remember the difference?

Think of what each one points you to. Here are three memory tricks:

1. The dictionary-and-map trick: A glossary is a mini dictionary. An index is a map.
2. The “gloss” link: A gloss is a short explanation of a word, so a glossary explains words. (A memory aid.)
3. The finger trick: Your index finger points, and the index points you to the page.

FAQ: Glossary vs Index

What is the difference between a glossary and an index?

A glossary lists specialized terms with their definitions, while an index lists topics, names and terms with the page numbers where they appear.

Do a glossary and an index both list items alphabetically?

Yes. Both are usually alphabetical, but a glossary gives definitions and an index gives page numbers.

Which comes first, a glossary or an index?

The glossary usually comes before the index, and the index is typically the last item in the book. Placement can vary by publisher and style guide.

Does a book need both a glossary and an index?

Not necessarily. Many nonfiction and academic books include both, while fiction rarely includes an index. Choose based on what your readers need.

What is the plural of index?

Both indexes and indices are used. Indexes is common for lists at the back of books, while indices is common in mathematics, science and finance.

Conclusion

When you’re weighing glossary vs index, remember that a glossary defines terms and an index points to pages. One works like a mini dictionary and the other like a map, and both usually sit in the back matter. Share this with someone who is writing a book or a thesis!