undefined is not a function

esta dando esse erro na chamado do jcycle.

<script type="text/javascript">
	$(document).ready(function(){
 $("#slider ul").cycle({ //o erro é nessa linha
 fx:'fade',
 speed: 2000,
 timeout: 3000
 });
	});
</script>

html

<div id="slider">
	<ul>
 <li>
 <img src="painel_admin/banner/01.jpg" />
 </li>
 <li>
 <img src="painel_admin/banner/02.jpg" />
 </li>
 <li>
 <img src="painel_admin/banner/03.jpg" />
 </li>
 <li>
 <img src="painel_admin/banner/04.jpg" />
 </li>
	</ul>
</div>