A transition is a relationship between two activities that represents workflow from activity to activity. Transitions provide the pathway between activities when modeling a workflow with an activity diagram. When a specific action in an activity is complete, the transition "fires" and the flow continues to the next activity. For example, you could have a source activity named "Take Order" and a destination activity named "Process Order" connected by a transition. When an employee takes an order, the transition moves the workflow along so that another employee can process the order.

Transitions commonly connect activities, send and receive signals, initial states, and final states. Transitions can also connect activities that reside within swimlanes.