Budget-Scope-Schedule
Those involved in projects will know the title refers to the ‘three-legged-stool’ of project management. And the answer always is, pick two, you can’t have all three.
There’s an argument that for every project, at some point along the way, the budget becomes central. It’s a rare project that is not under budget pressure, whether that is during the approval or financial investment decision point, or, later on when the project controls manager is producing reports that show the project is nowhere near meeting budget. So perhaps the three-legged-stool is misplaced. Meeting budget is always one of the two choices.