Use dollar sign for jQuery in WordPress

var $ = jQuery.noConflict();
$( ".whatever" ).hide();
(function($) {
	
	// $ Works! You can test it with next line if you like
	// console.log($);
	
})( jQuery );

Or include jQuery script in the header

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script>