tinymce not defined .. why ?

tinymce not defined .. why ?

I am trying to use TINYMCE richtextbox.

My html doc is HERE.

Now i have the following code for initialization:

  1. tinymce.init({
  2.     selector: '#description-textbox',
  3.     codesample_languages: [
  4.             {text: 'HTML/XML', value: 'markup'},
  5.             {text: 'JavaScript', value: 'javascript'},
  6.             {text: 'CSS', value: 'css'},
  7.             {text: 'PHP', value: 'php'}
  8.         ],
  9.     toolbar: "codesample"
  10. });
I get the following error:

Uncaught ReferenceError: tinymce is not defined
    at index.html:33

i have tinymce script in my document , so why am i getting this error ?

Thank you.
Gautam.