HTML <dfn> Tag
<dfn> tag represents the defining instance of a term.
The defining instance is the instance where the term is being described or defined. This is typically when the term is being used for the first time. There is no need to use the
<dfn> each time you refer to the term. You only need to use it at the point that the term is being defined.
<dfn> tag is written as
</dfn> with the term inserted between the start and end tags.
Basic tag usage
<dfn> Tag with Abbreviations
Abbreviations enclosed in the
<abbr> tag can include the abbreviation's expansion in the
title element. However, this expansion is not the defining instance. The
<abbr> tag can contain the expansion every time it appears in a document, but the defining instance (i.e. using the
<dfn> tag) should only appear once.
The following example demonstrates this. Note that the abbreviation and expansion appears twice, however the defining instance (i.e. using the
<dfn> tag) only appears once.
Attributes can be added to an HTML element to provide more information about how the element should appear or behave.
There are 3 kinds of attributes that you can add to your HTML tags: Element-specific, global, and event handler content attributes.
<dfn> element accepts the following attributes.
This table shows the attributes that are specific to the
|None, but the
The following attributes are standard across all HTML5 elements. Therefore, you can use these attributes with the
<dfn> tag , as well as with all other HTML tags.
For a full explanation of these attributes, see HTML 5 global attributes.
Event Handler Content Attributes
Event handler content attributes enable you to invoke a script from within your HTML. The script is invoked when a certain "event" occurs. Each event handler content attribute deals with a different event.
Below are the standard HTML5 event handler content attributes.
Again, you can use any of these with the
<dfn> element, as well as any other HTML5 element.
For a full explanation of these attributes, see HTML 5 event handler content attributes.
Differences Between HTML 4 & HTML 5
Here's a template for the
<dfn> tag with all available attributes for the tag (based on HTML5). These are grouped into attribute types, each type separated by a space. In many cases, you will probably only need one or two (if any) attributes. Simply remove the attributes you don't need.
title attribute has special semantics on the
<dfn> element. If used, then the exact value of the attribute is the term being defined.
Here are the official specifications for the
- HTML5 Specification (W3C)
- HTML Living Standard (WHATWG)
- Current W3C Draft (the next version that is currently being worked on)
- HTML 4 (W3C)
What's the Difference?
W3C creates "snapshot" specifications that don't change once defined. So the HTML5 specification won't change once it becomes an official recommendation. WHATWG on the other hand, develops a "living standard" that is updated on a regular basis. In general, you will probably find that the HTML living standard will be more closely aligned to the current W3C draft than to the HTML5 specification.