In project management a successor is an activity that follows another activity – not in the chronological sense but according to their dependency to each other. A successor activity can have several direct predecessor activities.
To determine the direct predecessors of an activity, you must clarify which activities you must complete before you can start the activity you’re currently looking at (reasons can be technical, organizational or methodological in nature).
To determine the direct successors, you must clarify which activities can only begin after you completed the current activity (reasons can be technical, organizational or methodological in nature).
Successors usually follow their predecessors in a chronological order, but there are some (very few) cases where the successor starts before its predecessor (start-to-end – see dependencies). This is a rare case however and it’s often hard to comprehend as it goes against our notion of time.