example.css

/*
<nav>
  <ul id="top-level">
    <ul id="dropdown">

    </ul>
  </ul>
  <ul id="top-level-2">

  </ul>
</nav>
*/

nav > ul {
  /* targets #top-level and #top-level-2 */
}

nav ul {
  /* targets #top-level, #top-level-2, and #dropdown */
}