Wordpress - jQuery

<script>
$(document).ready(function(){
$("button").click(function(){
alert("Hello");
// <===== **No space is allowed**
});
});
</script>

<button> Click me </button>

-------->
<script>
jQuery(document).ready(function($){
$("button").click(function(){
alert("Hello");
// <===== **No space is allowed**
});
});
</script>

<button> Click me </button>

------>
<script>
jQuery(document).ready(function(){
jQuery("button").click(function(){
alert("Hello");
// <===== **No space is allowed**
});
});
</script>

<button> Click me </button>