An activity is an operation or process consuming time and possibly other resources. An individual or work team can manage an activity. It is a measurable element of the total project programme.
The term ‘duration’ refers to the length of time needed to complete an activity.
The term 'path' refers to an activity or an unbroken sequence of activities in a project network. The critical path is the longest sequence of activities through a project network from start to finish, the sum of whose durations determines the overall project duration.
‘Float’ is the time available for an activity in addition to its planned duration. For more information see: Programme float.
‘Free float’ is the amount of time that an activity can be delayed beyond its early start/early finish dates without delaying the early start or early finish of any immediately following activity.
A hanging activity is an activity not linked to any preceding or successor activities.
'Impact' is the effect a change has on an activity or the effect a change to one activity has
on another activity.
Ref Society of Construction Law Delay and Disruption Protocol, 2nd edition, February 2017, published by the Society of Construction Law (UK). https://www.scl.org.uk/resources/delay-disruption-protocol
Earned Value Management Handbook, Published by the Association for Project Management in March 2013 suggests that: ‘…Each work package comprises a number of activities to be performed. Each activity can be assigned to only a single work package. Each activity is a stepping stone towards completion of its parent work package.’