Activity or Task Which one to use?

by Atul Gaur
Activity or Task

Activity and task are two project management terms often used interchangeably. This articles intends to highlight the difference between these two terms and their correct usage.


PMBOK 3rd edition defines activity as “A component of work performed during the course of a project”. A Google search on activity throws up some interesting definitions of the term the most appropriate definition with regard to project management is given by according to the site an activity is defined as “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”. 

Activities that are associated with achieving the project deliverables are called schedule activities. Each schedule activity is identified with a unique alpha numeric identifier. Identification of an activity helps in differentiating it from other project activities. Schedule activities have a description, which states the scope of work that needs to be performed on that schedule activity. All schedule activities have a defined start and finish date also called as estimated start and finish dates and an estimated duration. All schedule activities are logically linked to each other and can be represented on a network diagram called the schedule network diagram. The schedule network diagram can be analysed to predict the project completion date. The network diagram also revels the critical path and the critical activities for a project.

The logical relationship of schedule activity is based on its relationship with its immediate predecessor and successor activity which is known as activity dependency. All activities cannot happen at once and therefore each activity has a definitive lead and lag which is incorporated at the time of developing the schedule network.

Various resources are applied on schedule activities in order to achieve the completion of the schedule activities and each schedule activity has a cost associated with it. Schedule activities have assumptions and constraints which are taken into account while developing the network logic. All related schedule activities can be grouped under a common head called summary activity. No resources are assigned to summary activities and facilitates in reporting purposes.


PMBOK 3rd edition defines task as “A term for work whose meaning and placement with in a structured plan for project varies by the application area, industry, and brand for project management software”.  The definition of task as mentioned in is “The smallest identifiable and essential piece of a job that serves as a unit of work, and as a means of differentiating between the various components of a project”.

PMBOK in its definition itself suggests that “whose meaning varies” and depends on the “industry and the project management software” which means both these terms are interchangeable.

However according to me both these terms are different and the points of difference are duration, cost, logical relationship, resource consumption every task need not have a cost associated to it and need not be logically related to other activity/task for example coordination activities, conducting a  review meeting, solving problems are by definition tasks that a project manager performs in order to complete a schedule activity.

To avoid this confusion I stick to only one term and that is “activity”. How about you? 
Activity or Task Which one to use? Activity or Task Which one to use? Reviewed by Unknown on August 14, 2011 Rating: 5

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