:first-child

Examples

Only the first list item stands out:

<style>
  li:first-child { font-weight: bold; color: crimson; }
</style>
 
<ul>
  <li>First</li>
  <li>Second</li>
  <li>Third</li>
</ul>

Notes

The element must be first among all children, not just among elements of its type: if a heading comes before the paragraphs, p:first-child selects nothing. In that case use :first-of-type. :only-child matches an element that has no siblings.