Just as a note, jQuery is becoming less important now that Microsoft Internet Explorer 9 and newer editions is out. There's a great website on accomplishing things without jQuery if you don't need to support older Internet Explorer versions: http://youmightnotneedjquery.com/
And we don't cover jQuery at all (except a couple of pages in the appendix).
Jquery has a method/directive called 'noconflict' .
This is used in working with third party libraries that also use the '$' operator.
You can then use 'JQuery' ,ie. ,as library identifier or define a new symbol to identify the JQuery call.
And, the .noConflict() method does not need to be called in order to use the name jQuery -- that's always defined. What the method does is to restore the value of the name $ back to whatever it was before jQuery reassigned it to itself.