Pseudo-class :only-child

The :only-child pseudo-class represents an element that has a parent element and whose parent element has no other element children. Same as :first-child:last-child or :nth-child(1):nth-last-child(1), but with a lower specificity.

Syntax

selector:only-child{ properties }

Example

[style.css]

 em:only-child{
   background-color: yellow;
 }

[index.html]

<body>
  <h1>Only-child example</h1>
  <p>This is a <em>paragraph</em>.</p>
  <p>This is a paragraph.</p>
</body>

The CSS Selectors Level 3 specification defines the :only-child pseudo-class selector in 6.6.5.10. :only-child pseudo-class.