Wrap definition items in a definition list

Rule Details

The <dt> (description term) and <dd> (description details) elements are only semantically valid when used as children of a <dl> (description list).

Code Example

<!-- ✅ Good: Properly wrapped -->
&lt;dl&gt;
  &lt;dt&gt;Term</dt>
  &lt;dd&gt;The definition of the term.</dd>
</dl>
 
<!-- ❌ Bad: Orphaned elements -->
&lt;dt&gt;Orphaned Term</dt>
&lt;dd&gt;This is not inside a list.</dd>
 
<!-- ❌ Bad: Using other containers incorrectly -->
<ul>
  <li>
    &lt;dt&gt;Invalid usage</dt> <!-- dt cannot be a child of li or ul -->
  </li>
</ul>

Why It Matters

• Relationship Mapping: Browsers use the <dl> container to associate specific terms with their corresponding descriptions.
• Accessibility Tree: Assistive technologies expose these elements as a "list" only when wrapped correctly, allowing users to navigate by list items.
• Validation: Improperly nested elements will fail HTML validation, which can lead to unpredictable rendering issues.

Best Practices

✅ Always use <dl>: Never use <dt> or <dd> on their own for styling purposes. ✅ Logical Order: Typically, <dt> comes before its associated <dd>. ✅ Multiple Details: It is perfectly valid to have one <dt> followed by multiple <dd> elements for a single term.

Tools & Validation

• W3C HTML Validator (opens in new tab)
• Axe-core Rule: definition-list-item (opens in new tab)

Exceptions

• Simple data tables can sometimes fail more from missing header relationships than from missing enhancements such as captions or mobile wrappers, so prioritize the strongest semantic issue.
• Do not convert layout structures into data-table markup just to satisfy a rule; the correct fix may be to remove table semantics entirely.
• When several table-accessibility issues overlap, resolve the header-cell relationship first because downstream announcements depend on it.

Standards

• Align the implementation with W3C WAI: WCAG Overview and verify the rendered experience, not only the source code.
• Align the implementation with MDN: Accessibility and verify the rendered experience, not only the source code.

Verification

Automated Checks

• Inspect the browser accessibility tree or accessibility pane for the relevant element, role, or accessible name.
• Run an automated accessibility checker such as axe or Lighthouse where applicable.

Manual Checks

• Test the affected UI with keyboard-only navigation and confirm the rule holds in the rendered experience.
• Re-test one representative user flow with a screen reader if this rule affects a key interaction.