A Constraint is 1) a specific limitation placed on the project schedule to regulate the start or finish dates of a task or activity. Any factor that affects when an activity can be scheduled. The Constraint can affect the start, completion, or duration of a scheduled activity. Schedule constraints are used to impose limits on the work items to prevent certain activities from being started too early or finished too late; 2) a degree of statistical dependence between or among variables that controls what to do by keeping within particular limits.

Related Definitions in the Project: The Project Controls