Scope Control

Scope control is one of the keys to effective project management. Good project management requires managing scope in such a way that the goals of a project can be obtained on time without leaving out resolution of items that are critical to the project’s success. Good scope control allows the changing and adding of critical tasks without adding in unnecessary items or items that would be best suited for a later version that if added could cause a project to miss it’s critical deadlines.
Determining which items need to be addressed during a successful project, is crucial to successful scope control and positive project outcome. It is imperative that a project manager maintain flexibility by changing and adding tasks that will make or break a project’s success. However, items that are not critical to a successful delivery or that may be better suited to a phase two release or follow up version should be barred from current project scope, especially if completion of the items threatens an on time delivery or implementation goals of the project.
Good scope control, therefore is critical to project management and must be managed with a balance of flexibility for critical items and rigidity against adding superfluous “bells and whistles”.

This term is defined in the 3rd and the 4th edition of the PMBOK.