JQuery Error: $ is not defined (index)

[zacca94]

<script>$('#quickLogin').submit(
	function () {
		var email	 = $('#email');
		var password = $('#password');
		var referer  = $('#referer');
		var session  = $('#session');
		var result	 = $('.result');
		var error	 = false;
		
		// Check the e-mail values is empty or incorrect
		if (!form.isValidEmail(email.val)) {
			$("#form_email").show();
			error = true;
		}
		
		// Check the password values is empty
		if (!form.isValidPassword(password.val)) {
			$("#form_password").show();
			error = true;
		}
		
		// Send the credential values to another xml.php?action=login using AJAX in POST menthod
		if (!error) {
			$.ajax(
				{
					type	: 'POST',
					dataType: 'json',
					data	: 's=' + session.val + '&email=' + email.val + '&password=' + password.val + '&referer=' + referer.val,
					url		: '<?php echo $var['base_url'] ?>includes/ajax.php?form=login',
					success	: function (response) {
						switch (response) {
							case 'success': {
								window.location = '<?php echo $var['base_url'] ?>' + referer.val;
							}
							break;
							
							case 'error': {
								result.html('<div>' + response.error + '</div>');
							}
							break;
							
							default: {
								result.html('Ajax error');
							}
						}
					}
				}
			);
		}
		
		return false;
	}
);
</script>

Console error: Uncaught ReferenceError: $ is not defined (index):142(anonymous function) (index):142

La linea corrisponde allo spazio vuoto prima di <script>