The
<dfn>tag identifies the defining instance of a term or concept within a document.
It is used the first time a term appears, usually alongside its explanation. Browsers may style it in italics by default, but the real purpose is semantic — helping search engines, accessibility tools, and documentation systems understand term definitions.
Syntax
<dfn>term being defined</dfn>Attributes
| Attribute | Description | Value |
|---|---|---|
| None | The <dfn> tag has no specific attributes. | — |
Example
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>DFN Tag Example</title>
</head>
<body>
<p>
<dfn>HTML</dfn> is a markup language used to structure content on the web.
</p>
</body>
</html>Output
Browser Output
Use our Tryit Editor to see the output
Browser Support
 Chrome |  Firefox |  Edge |  Safari |  Opera |  IE9+ |
|---|---|---|---|---|---|
| ✅Yes | ✅Yes | ✅Yes | ✅Yes | ✅Yes | ✅Yes |
Notes
<dfn>marks only the defining occurrence of a term — later references should not use<dfn>.- Screen readers may announce it as a “definition”, improving accessibility.
- Often combined with
<abbr>when defining abbreviations. - Purely semantic — does not add styling unless styled with CSS.
Conclusion
The <dfn> tag adds meaningful structure by identifying the first definition of a term in your content. It’s simple but valuable for documentation, accessibility, and SEO. Use it whenever you introduce important vocabulary or concepts.
