The **`<dfn>` tag** is used as a definition element that specifies the title of a definition. The definition of the title specified by `<dfn>` tag must follow the announcing tag. 

# Attributes
The `<dfn>` tag supports #key# global attributes: attributes common to all HTML elements, e.g., class, id, lang, title, etc. #key# and #key# event attributes: attributes connected to action events, e.g., a user clicks a piece of text. #key#. 

# Content of tag
The content of the tag can modify the definition title. Some examples are:
- **Definition only** 
To italicize the definition's title only, use the `<dfn>` tag without any other tags. 
- **Add a title** 
The `<dfn>` tag can include a `title` property. The value of this title is the term being defined.
- **Abbreviated title** 
If the title is an abbreviation explained in the definition, you can use the `<abbr>` tag to show what the abbreviation stands for. Hovering the cursor over the title will show the un-abbreviated title.
- **Refer back to the title** 
The `<dfn>` tag can be used to specify a hyperlink within the text. The `<a>` tag is used to refer to the `<id>` specified in the content of `<dfn>` tag.

These modifications are also explained in the code below.

# Code 
The following code snippet shows the different ways the `<dfn>` tag can be used.

<html>
 <head>
 </head>
 <body>
 
 <dfn>CSS</dfn> is used to style HTML pages. (simple case) 

 
 <dfn title="Cascading Style Sheets"> CSS </dfn> is used to style HTML pages. (title added)

 
 <dfn><abbr title="Cascading Style Sheets">CSS</abbr></dfn> is used to style HTML pages. (abbreviation case)

 
 <dfn id="css-def">CSS</dfn> is used to style HTML pages. (linked text)
 This is some filler text...
 Learn <a href="#css-def">CSS</a> today!
 </body>
</html>

codemirror

What is the <dfn> element in HTML?

The  tag is used as a definition element that specifies the title of a definition. The definition of the title specified by  tag must follow the announcing tag. Attributes The  tag supports global attributesattributes common to all HTML elements, e.g., class, id, lang, title, etc. and event attributesattributes connected to action events, e.g., a user clicks a piece of text..   Content of tag The content of the tag can modify the definition title. Some examples are:  Definition only  To italicize the definition s title only, use the  tag without any other tags. Add a title  The  tag can include a title property. The value of this title is the term being defined. Abbreviated title  If the title is an abbreviation explained in the definition, you can use the  tag to show what the abbreviation stands for. Hovering the cursor over the title will show the un-abbreviated title. Refer back to the title  The  tag can be used to specify a hyperlink within the text. The  tag is used to refer to the  specified in the content of  tag.  These modifications are also explained in the code below. Code The following code snippet shows the different ways the  tag can be used. 