Simple jQuery not working using .css and .js files from jQueryUI download.

Simple jQuery not working using .css and .js files from jQueryUI download.

The following is my basic js/jquery code, within HTML, which should 'fire'
  2. <script type="text/javascript">
  3.   S(document).ready(function(){

  5.     $( "#date" ).datepicker();
  6.   alert ("hello");
  7.   $('#my-tabs').tabs();
  8.   });
  9. </script>
However ( the alert has been added, just to check the function is running, but it's not ) my HTML is not being styled, N.B. the 'id' variable tag names are definitely right for my elements. The references to the relevant .css and .js files are as follows ...
  2. <head>
  3.   <meta charset="utf-8">
  4.   <title>My New Page Design</title>
  5.   <link rel="stylesheet" type="text/css" href="jquery-ui.min.css">
  6.   <script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
  7.   <script type="text/javascript" src="jquery-ui.min.js"></script>
  8.  </head>
The file-paths should be OK too, i.e. the files are in the same directory, as my HTML page ( index.html ). Any thoughts ? Thanks.