# Glossary
Create a `GLOSSARY.md` file in your book's root to define terms. These terms are automatically detected and displayed as tooltips throughout your book.
## Format
```markdown
## API
Application Programming Interface
## HTML
HyperText Markup Language
## SSR
Server-Side Rendering
```
Each term starts with `## Term` followed by its definition on the next line.
## How It Works
When guidebook builds your book, it scans all pages for glossary terms and wraps them in tooltip spans:
```html
<span class="glossary-term" data-definition="Application Programming Interface">API</span>
```
Hovering over a term shows its definition.
## Exclusions
Terms are **not** replaced inside:
- Code blocks (`` ` `` and ` ``` `)
- Links (`<a>` tags)
- Headings (`<h1>` through `<h6>`)
- Script tags
- Elements with `class="no-glossary"`
To prevent replacement in a specific element, add the `no-glossary` class:
```html
<span class="no-glossary">API</span>
```