| 01 | Beginning Activity Starting activity for a project plan |
| 02 | Ending Activity Finish activity for a project plan |
| 03 | Activity Generic activity or work task |
| 04 | Interface Activity (when 2 or more separate networks are combined to create 1 network) An activity that links one or more separate, but related, project plans |
| 05 | Summary Activity An activity that sums the amount of time (and resources) for lower level tasks or activities |
| 06 | Milestone A specific event or deliverable item |
| 07 | Event A specific end result or deliverable item |
| 08 | Constraint - Finish to Start A relationship type for activities - the succeeding activity can't start until the preceding activity is complete |
| 09 | Constraint - Start to Finish A relationship type for activities - the preceding activity can't start until the succeeding activity is finished |
| 10 | Constraint - Finish to Finish A relationship type for activities - the preceding activity can't finish until the succeeding activity is finished |
| 11 | Constraint - Start to Start A relationship type for activities - the preceding activity can't start until the succeeding activity starts |
| 12 | Constraint - Dummy A relationship type for activities to show interdependency between two activities on arrow diagram method activities |
| 20 | Cost Account Activity An activity with an assigned cost account number |
| 21 | Work Package Activity An activity with an assigned work package number |
| 22 | Data Item An assigned data item effort, task, or activity |
| ZZ | Mutually Defined |