Lonely vs. Loneliness

In my mind there is a difference between being alone and being lonely.  There are often days that I spend by myself and I have fun.  It can be nice to hear your own thoughts and be able to reflect on them without anyone else around.  It does get kind of lonesome when you haven't seen any of your family or friends in awhile, but it's a loneliness I feel that I can handle.  I've felt the loneliest when I'm with people who put me down and hurt me, or when I'm in a crowd of people and everyone seems happy and I'm just standing there...Alone.