<dfn>

The HTML <dfn> element represents the defining instance of a term.

Content categories	Flow content, phrasing content, palpable content.
Permitted content	Phrasing content, but no <dfn> element must be a descendant.
Tag omission	None, both the starting and ending tag are mandatory.
Permitted parents	Any element that accepts phrasing content.
Permitted ARIA roles	Any
DOM interface	HTMLElement

Attributes

This element's attributes include the global attributes.

In HTML5, the title attribute has special meaning, as noted above.

Usage notes

• The <dfn> element marks the term being defined; the definition of the term should be given by the surrounding <p>, <section> or definition list group (usually a <dt>, <dd> pair).
• The exact value of the term being defined is determined by the following rules:
  1. If the <dfn> element has a title attribute, then the term is the value of that attribute.
  2. Else, if it contains only an <abbr> element with a title attribute, then the term is the value of that attribute.
  3. Otherwise, the text content of the <dfn> element is the term being defined.

Examples

The following examples are valid in HTML5.

<!-- Define "The Internet" -->
<p><dfn id="def-internet">The Internet</dfn> is a global
system of interconnected networks that use the Internet
Protocol Suite (TCP/IP) to serve billions of users
worldwide.</p>

Later in the same document:

<dl>
  <!-- Define "World-Wide Web" and reference
       definition for "the Internet" -->
  <dt>
    <dfn>
      <abbr title="World-Wide Web">WWW</abbr>
    </dfn>
  </dt>
  <dd>The World-Wide Web (WWW) is a system of
  interlinked hypertext documents accessed on
  <a href="#def-internet">the Internet</a>.</dd>
</dl>

Result

Specifications

Specification	Status	Comment
WHATWG HTML Living Standard The definition of '<dfn>' in that specification.	Living Standard
HTML5 The definition of '<dfn>' in that specification.	Recommendation
HTML 4.01 Specification The definition of '<dfn>' in that specification.	Recommendation

Browser compatibility

See also

• Elements related to definition lists: <dl>, <dt>, <dd>
• <abbr>