I had always thought that punishment was something that was just that, punishment. The point being that the sub or slave has done something that transcend a rule that was agreed to prior to the event happening. As such, punishment does not need to be physical pain but something that the slave or sub would view as punishment. For example, if no contact for a specified period of time could be punishment. If the slave or sub enjoyed the act, why would this be punishment. For me punisment has a specific purpose and should not be confusing. Dealing with behavior improvement perhaps could be viewed as discipline.
Sir Dred