How can you use subclasses in W3.CSS?

Question :

How can you use subclasses in W3.CSS?

<div class="w3-row">
<div class="w3-col s2 m4 l3">
  <p>The text use 2 columns on small screen, 4 on a medium screen and 3 on a large screen</p>
 </div>
</div>