<dfn> is a tag used in HTML to mark the definition of a term, representing "definition term". It is often used in conjunction with explanation when the term first appears to improve semantics and accessibility. 1. <dfn> is used to label professional terms, abbreviations or uncommon vocabulary definitions; 2. It is often used with <abbr> to enhance semantic clarity; 3. It is displayed in italics by default, but can be customized with CSS; 4. It should only be used when it first appears to avoid abuse affecting readability; 5. Explanation text should not be wrapped, but the term itself is irreplaceable for emphasis labels.
The <dfn></dfn>
element is used in HTML to mark a definition of a term, which stands for "definition term". This tag comes in handy when you want to emphasize the first appearance of a word on the page and give it an explanation at the same time.

Basic use: marking term definition
The most common use scenario is when a professional term, abbreviation, or less common vocabulary is first mentioned in a paragraph, and is used in conjunction with explanations. for example:
<p>HTML's full name is <dfn title="Hypertext Markup Language">HTML</dfn>, which is the basis for building web pages. </p>
Browsers usually display the content in <dfn>
in italics (default style), but the specific performance depends on the CSS settings.

Use more clearly with <abbr>
If you are defining an abbreviation, you can use it in conjunction with the <abbr>
tag. This makes the semantics clearer and more friendly to screen readers:
<p><dfn><abbr title="Cascading Style Sheet">CSS</abbr></dfn> is a language used to describe web page styles. </p>
This approach not only helps accessibility, but also allows search engines to better understand the context.

Practical application suggestions
- Use
<dfn></dfn>
only when the term first appears to avoid repeated abuse. - If further explanation is required for the term meaning, detailed explanations can be added in the same paragraph or near.
- Provides additional help with
title
attributes or JavaScript tooltips. - You can customize the style through CSS, such as removing italics, bolding, or changing the color.
Things to note
-
<dfn></dfn>
should wrap the actual term itself, not the explanatory text. - Not to emphasize the key points, nor is it a
<em></em>
or<strong></strong>
label. - Do not overuse the page to avoid affecting readability and semantic clarity.
Basically that's it. Rational use of <dfn></dfn>
can improve the semantic structure of the page. Although it is not often paid attention to, it is still quite useful in details.
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