Problém s JS

Dobrý den, mám takový problém s Javascriptem. Vůbec nereaguje na webových stránkách a v prohlížeči google chrome když dám Console tak mi vypisuje hlášku: Uncaught ReferenceError: $ is not defined at index.html:10. Prosím o radu.

Celý JavaScript(je nalinkovaný jako externí soubor v html):

     $(document).ready(function() {
       $('.open-overlay').css('pointer-events', 'none');
       var overlay_navigation = $('.overlay-navigation'),
         top_bar = $('.bar-top'),
         middle_bar = $('.bar-middle'),
         bottom_bar = $('.bar-bottom');

       overlay_navigation.toggleClass('overlay-active');
       if (overlay_navigation.hasClass('overlay-active')) {

         top_bar.removeClass('animate-out-top-bar').addClas s('animate-top-bar');
         middle_bar.removeClass('animate-out-middle-bar').a ddClass('animate-middle-bar');
         bottom_bar.removeClass('animate-out-bottom-bar').a ddClass('animate-bottom-bar');
         overlay_navigation.removeClass('overlay-slide-up') .addClass('overlay-slide-down')
         overlay_navigation.velocity('transition.slideLeftI n', {
           duration: 300,
           delay: 0,
           begin: function() {
             $('nav ul li').velocity('transition.perspectiveLeftIn', {
               stagger: 150,
               delay: 0,
               complete: function() {
                 $('nav ul li a').velocity({
                   opacity: [1, 0],
                 }, {
                   delay: 10,
                   duration: 140
                 });
                 $('.open-overlay').css('pointer-events', 'auto');
               }
             })
           }
         })

       } else {
         $('.open-overlay').css('pointer-events', 'none');
         top_bar.removeClass('animate-top-bar').addClass('a nimate-out-top-bar');
         middle_bar.removeClass('animate-middle-bar').addCl ass('animate-out-middle-bar');
         bottom_bar.removeClass('animate-bottom-bar').addCl ass('animate-out-bottom-bar');
         overlay_navigation.removeClass('overlay-slide-down ').addClass('overlay-slide-up')
         $('nav ul li').velocity('transition.perspectiveRightOut', {
           stagger: 150,
           delay: 0,
           complete: function() {
             overlay_navigation.velocity('transition.fadeOut', {
               delay: 0,
               duration: 300,
               complete: function() {
                 $('nav ul li a').velocity({
                   opacity: [0, 1],
                 }, {
                   delay: 0,
                   duration: 50
                 });
                 $('.open-overlay').css('pointer-events', 'auto');
               }
             });
           }
         })
       }
     })