Statement Of Work - Documentation that is used to describe the exact work that will be performed. Used in a business setting, the action of performing a task for a specified amount of money is placed into a SOW. This SOW described exactly what will be performed for that amount of money. Anything outside of the Statement of Work could be negotiated but more or less a new SOW would have to be drafted creating a new task.
A SOW was drafted to build 3 flash banners and it was completed according to the SOW. The client has additional changes to the banners so a new SOW would have to be drafted.