A graphical method for showing dependencies between tasks (activities) in a project. The network consists of nodes connected by arcs. Nodes denote events and represent the culmination of one or more activities. Arcs represent activities and are labelled with the name of the activity and have an estimated time to complete the activity. Dummy unlabelled arcs with zero completion time are used to fan out from one event to other dependent events. Before progress can be made from one event to another, all activities leading to that event must have been completed. The longest path through the activity network gives the completion time for the project represented by the network. See also critical path method, PERT chart.