Activity: A defined unit of work performed during the course of a project that is described using a verb. An activity normally has a work description, expected duration, expected cost, and expected resource requirements. Activity and task are terms that are often used interchangeably.

Control account (CA): A specific WBS work element and functional organizational responsibility where the work in a work package is assigned and actual direct labor, material, and other direct cost data can be collected; formerly known as a cost account in earned value management systems.

Cross-cutting element: A WBS element that relates to work performed in other branches of the WBS. For example, the work performed in project management relates to other work in the project yet has its own unique identity.

Deliverable: Any tangible, verifiable product, service, or result that must be produced to complete a project or part of a project. The term is often used narrowly to refer to hardware or equipment, a report, software, data, or other items that are subject to approval by the project sponsor or customer.

End items: A general term that represents the hardware, services, equipment, facilities, and data that are deliverable to the customer or that constitute a commitment on the part of the project manager to the customer.

Organizational breakdown structure (OBS): A graphic representation of the work of a project in terms of organizational units.

Portfolio: A collection of related projects or programs and other work that groups projects or programs to support effective management of the total work effort in a way that meets strategic business or organizational objectives.

Program: A long-term undertaking consisting of a group of related projects that are managed in a harmonized way. Programs often include an element of ongoing work or work related to the program deliverables.

Project: A temporary endeavor undertaken to create a unique product, service, or result.

Project element: A component of the work to be performed in a project derived from the logical decomposition of the total work (top down) or synthesis of a logical grouping of required activities or work elements (bottom up).

Responsibility assignment matrix (RAM): A graphic structure that correlates the work outlined in a WBS element to the organizational division that is responsible for the effort. A RAM is created by intersecting the WBS with the OBS. The control account is established at the intersection.

Risk breakdown structure (RBS): A hierarchical arrangement of the risks that have been identified in a project or a hierarchical framework presenting possible sources of risk, either generic or project specific.

Subproject: A logical major component of a project. A subproject is usually a WBS element that can be managed as a semi-independent component of the project and is the responsibility of one person or organization.

Task: A generic term for a defined unit of effort on a project; often used interchangeably with activity, but could be a further breakdown of an activity. A task, like an activity, has an action component and is defined using a verb.

Work breakdown structure (WBS): A product-oriented, service-oriented, or result-oriented family tree or grouping of project elements that organizes and defines the total work scope of the project. Each descending parent/child level represents an increasingly detailed definition of the project work.

WBS dictionary: A document that describes in brief narrative format what work is performed in each WBS element.

WBS element: An entry in the WBS that can be at any level and is described by a noun or a noun and an adjective.

WBS level: The relative rank of a WBS element in a WBS hierarchy. Customarily the top rank, the total project, is Level 1 and the top element in a program is Level 0.

Work element: Same as WBS element.

Work package: The lowest-level element in each branch of the WBS. A work package provides a logical basis for defining activities or assigning responsibility to a specific person or organization. Also, the work required to complete a specific job or process such as a report, a design, a documentation requirement or portion thereof, a piece of hardware, or a service.

100 percent rule: The requirement in a WBS that the sum of the work effort of a series of child elements add up to 100 percent of the work effort of the parent element.