What is the difference between being alone and lonely?

Who can answer this question for me? What is the difference between being alone and being lonely when you are married? I have been pondering this question for some time now and I have no clue. Well..not quite true I do know the difference but I guess I want I really want to know is what each person's definition of this question means to them. To me, being alone is you don't have anyone in your life that you can count on, talk to, or even depend on. So is being lonely just the opposite? What do you do when you are feeling lonely? Who do you turn to? Is it your best friend? Your family? Your co-worker? Your spouse? or someone you happen to find that fills that missing void in your life and it develops into something more than you can handle? For some of us it's the later of all situations. Is it sad that you turn to someone else? I don't know...