Uncaught referenceError: JQuery is not defined

Uncaught referenceError: JQuery is not defined

Dear,

tried alot of things but cannot get this error away, This is my code:

this is my <head>
<script type= "text/javascript" src= "js/modernizr.custom.js" > </script >
<script src= "js.jquery.royalslider.min.js" > </script >

this is at the end of my page
<script >
jQuery( document). ready( function( $) {
Uncaught ReferenceError: jQuery is not defined
$( "#royalSlider"). royalSlider({
// options go here
// as an example, enable keyboard arrows nav
keyboardNavEnabled: true
});
});
</script >
<script src= "js/jquery-1.9.1.min.js" type= "text/javascript" > </script >
<script src= "js/jquery.scrollto.js" type= "text/javascript" > </script >
<script src= "js/waypoints.min.js" type= "text/javascript" > </script >
<script src= "js/jquery.tweet.js" type= "text/javascript" > </script >
<script src= "js/scripts.js" type= "text/javascript" > </script >
<script src= "js/grid.js" > </script >