Which Is Correct: Task or Activity?

There are several phases in a project. For example preparation, implementation and completion. Each phase contains different work packages. Depending on the size of the project and the individual style of the project manager, these work packages can be further broken down into individual tasks. This brings us to the tasks and activities.

In this context, many terms are used for one and the same purpose like operation, task, activity, etc.

In Merlin Project we decided to use the term activity - mainly because of our proximity to PMI and the PMBOK.