The state, quality, or sense of being restricted to a given course of action on inaction. An applicable restriction or limitation, either internal or external, to the project that will affect the performance of the project or a process. For example, a schedule constraint is any limitation or restraint placed on the project schedule that affects when a schedule activity can be scheduled, and is usually in the form of fixed imposed dates. A cost constraint is any limitation or restraint placed on the project budget, such as funds available over time. A project resource constraint is any limitation or restraint placed on resource usage, such as what resource skills or disciplines are available, and the amount of a given resource available during a specified time frame.