How To Add Transition Duration To A Dropdown Css Menu?

I just wanted to know if it is possible to add a transition duration to a dropdown menu. I have been looking for an answer online for a while but all I could find is some bootstrap and javascript codes in order to execute this feature.

 <li class="dropdown"><a href="#" class="dropbtn">Dropdown</a>
                    <div class="dropdown-content">
                       <a href="#">Houses</a>
                       <a href="#">Catles</a>
                       <a href="#">Studios</a>
                    </div>
            </li>