The arrow diagramming method (ADM) refers to a schedule network diagramming technique in which the schedule activites within a given project are represented by the use of arrows. The beginning of the schedule activity is represented by the tail, or base, of the arrow. The pointed end of the arrow represents the endpoint of a specific schedule activity, and the length of the arrow can loosely represent the time in between (although, it should be noted that the length should not be interpreted as any literal measure as to the time expected for the schedule activity to take to complete, as often these arrows are scaled to fit in the presentation of chart that is being populated). The points at which these schedule activities are to be connected are referred to as nodes. The connection of these schedule activities is done to demonstrate the sequence or order in which these activities should take place, and this connect point, or node, is usually represented by a small circle or sphere. See also precedence diagramming method.
This term is defined in the 3rd edition of the PMBOK but not in the 4th and 5th.