jQuery Undefined - $ ( document ).ready(function()

jQuery Undefined - $ ( document ).ready(function()

Hi Guys,
I'm pretty new to jQuery, but am OK with HTML. Here's my problem that I cannot solve.
my index.html works fine. Shows on browser exactly as I want it to.
However, when I create a html .doc from a file ie /destinations/europe/algarve/hotel.html
a message comes up as jQuery undefined and the whole page is all Blue text on the left hand side in a row with no images etc.
I have searched Youtube, Google the lot but still cannot see what I have to put in or under or where the $ (document) .ready (); goes or what to do with it.
Please help as I have little of my hair left to pull out
Thanks
Jay