In its original form, the term "addiction" referred to substances only, where biochemical changes, tolerance and withdrawal effects could easily be measured. As the usage has spread to behaviors (internet, sex, spending, etc.), the meaning has become more fuzzy. On the subject of internet use, do we just use the familiar definition of any disorder... that it must interfere with normal life functioning? Is there a difference between those of us who need to be online many hours for work, and those who just surf the net, or spend hours in chat rooms?