1. General: Measurable amount of work performed to convert inputs into outputs.
2. Activity based costing (ABC): Aggregations of actions performed in an organization which are useful for ABC computations.
3. Project management: Smallest unit of work having four characteristics: (1) definite duration, (2) logic relationships with other activities in the project, (3) resource consumption, and (4) an associated cost. Often used as an alternative term for task.