The Triple Constraint of Time-Cost-Scope contains the key attributes which need to be managed for the successful completion of any project.
Time – estimation of the time required to produce a deliverable
Cost – estimation of the amount of money required to complete the project
Scope – the elements that, when completed, make up the deliverables on the project.
Being a triangle, one cannot adjust one side without altering the other sides; i.e. they are inter-related.