A constraint is something that limits or controls what you can do. Synonyms include restriction, check, curb, and limitation.
Nearly every project is constrained in some way with restrictions or limitations that may be either external or internal the project.
While these constraints may come from many directions, there are at least six constraints common to every project.
They are:
Scope: Defines exactly what is and is not to be included in the project.
Cost: This is the budget funding for the project that must not be exceeded.
Schedule: This is the expected dates for interim project deliveries and/or project completion.
Quality: Defines the criteria by which the project deliverables will be measured against the approved project scope.
Resources: Will the material or human resources required to achieve the project scope be available when needed.
Stakeholder Satisfaction: Defines the goals or objectives that must be accomplished for the stakeholders to be satisfied.