modal is not a function error in jquery code example

Example: Uncaught TypeError: $(...).dialog is not a function at Calendar.eventClick ((index):52)

<script src="https://code.jquery.com/jquery-1.11.1.min.js"></script>
 
<script src="https://code.jquery.com/ui/1.11.1/jquery-ui.min.js"></script>

<link rel="stylesheet" href="https://code.jquery.com/ui/1.11.1/themes/smoothness/jquery-ui.css" />

<button id="opener">open the dialog</button>
<div id="dialog1" title="Dialog Title" hidden="hidden">I'm a dialog</div>