The <dfn> HTML element is used to indicate the defining instance of a term within a document. It is a semantic element that helps browsers and assistive technologies understand that the enclosed text is the term being defined. This element is particularly useful in educational or technical content where precise definitions are necessary for clarity and understanding. By using the <dfn> tag, authors can highlight terms that are being defined, enhancing the semantic structure and accessibility of the document.
The <dfn> element is typically used in a sentence where the term is being defined for the first time. It can be paired with the title attribute to provide additional context or information about the term, although this is not a common practice. The text inside the <dfn> element is usually styled in italics by default, but this can be customized with CSS. Here is an example of how the <dfn> tag can be used:
<p>The Web Content Accessibility Guidelines require that non-text content has a text alternative. <dfn>Non-text content</dfn> is content that is not a sequence of characters that can be programmatically determined or where the sequence is not expressing something in human language.</p>Valid Attributes for <dfn>
The <dfn> element does not have specific attributes beyond the global attributes, which include:
| Attribute | Description |
|---|---|
| class | Specifies one or more class names for the element, used for CSS styling. |
| id | Defines a unique identifier for the element, useful for linking and JavaScript. |
| style | Contains inline CSS styles for the element. |
| title | Provides additional information about the element, often displayed as a tooltip. |
In summary, the <dfn> element is a valuable tool for marking up definitions of terms, improving both the semantic clarity and accessibility of web content. It is especially beneficial in contexts where understanding specific terminology is crucial, such as technical documentation or educational materials.