Terminal element
In project management, a terminal element is the lowest element (activity or deliverable) in a work breakdown structure(WBS); it is not further subdivided.
Terminal elements are the items that are estimated in terms of resource requirements, budget and duration, linked by dependencies and scheduled.
A terminal element is sometimes called a work package, although the two terms are not synonymous.
See also:
In category theory, a terminal object is sometimes called a terminal element. A terminal object of a category has the property that every object in the category (including itself) has exactly one arrow leading to it.