jQuery: Using jQuery with Other Libraries

Ever faced a problem to use jQuery with other Library ?
By default, jQuery uses "$" as a shortcut for "jQuery"

jQuery provides the convenience by defining our own shortcut which eliminates the conflict.
A simple example

<script src="jquery.js"> </script>
<script src="prototype.js"> </script>

<script type="text/javascript" >
jQuery.noConflict()  //now by default, $ is jQuery.
  //But you can reassign it to your own variable.
    var $jq = jQuery;
    //start using $jq for jquery's $
    $jq(document).ready(function() {
    $jq("div").hide();    });
</script>