The concept of discrete effort applies directly to the specific work efforts that can be directly traced and identified as having a direct tie to ultimate completion of the project-related work breakdown structure components as well as the deliverables. It is essential that all of these efforts be directly measurable. To elaborate on this term, certain elements of the life of a project, and certain work components, while offering great assistance in the advancement of the project, may not directly tie in to the ultimate completion of the project. These specific components, regardless of their measurability, cannot be considered discrete work efforts because their can be no direct tie or link to these components and the ultimate completion of the project. However, if a specific component serves the dual purpose of providing assistance to the project team as well as providing a direct link to the ultimate completion, and it is measurable, then it can be considered discrete effort. The term discrete effort can be directly contracted to that of apportioned effort.
This term is defined in the 3rd edition of the PMBOK but not in the 4th.